I won't waste your time with a detailed battle plans for every little skirmish, and namely the opening minicampaigns will be described without
unnecessary details.
Latium (the first minicampaign):
Pretty straightforward. Dismiss all your starting units and get the Auxilia. Keep them with the Legate. You shouldn't even heal them for the whole minicampaign; maybe you won't even lose a single guy until the last scenario.
You'll win the
first two scenarios without any problems. There's no reason to do anything during the
Sabine Ambush. You won't be given any experiences for the killed enemy men. Just hide, so that you don't lose someone.
Don't purchase pincushions until the
Scout the Etruscans, where you'd wish to get rid of the enemy Skirmishers, so that they don't hurt your core guys too much. Either you may TDT them with Scouts, or attack them with Velites. No matter what, you need to either kill them or at least let them waste the ammo. Then the Auxilia will eat the enemy alive and won't even spill the bones, so your only goal is to not lose Legate. And it's an easy task.
You may also try to win with just the Auxies, to gain more experiences. But well, we're playing a wargame, not a lottery, so...
The Early Republic (the second minicampaign):
"The Roman Republic was established when Lucius Tarquinius Superbus, the 7th and last Etruscan King of Rome, was overthrown after his son raped Lucretia."
You're entering this minicam with a Legate at level seven to nine, Auxilia at level three and 315 Denarii. Purchase the second Auxilia squad for three hundred gold, and buy yourself a drink for the remaining fifteen Denarii.
Legate should have some mix of tactics and combat skills - after all, your army is too little to a) not use Legate as a real unit and b) to need many order points.
Hide your unis in the SE forest during the
Aequi Riders. When I'm in a mood to bother myself, I try to TDT few Skirms with a Legate, but well... you know...
So just wait in a defensive line and let the enemy units break on your superior men. I wouldn't try to capture the Skrims in the open, as the enemy Scouts may do the same to your Auxilia.
Hernici Farmers is completely the same, just wait for the enemy to come. Two Auxilias are enough to win this fight.
It's quite possible that your Auxies will bloody their noses a bit. They'd still do better than the Legate.

There's a very solid tactic for
Coriolanus. Purchase Scouts and let them wear green T-shirts, so that their icon matches their colour. This is very important...
Then hide the Auxilias together with the Legate in the forest. Set Scouts to defensive formation and charge one of the Skirmishers. TDT them (it is quite important to get away from the central heavies, so that they don't interact), than TDT the second Skirmishers. Then finally provoke both the central Spearmen, take care to not provoke the enemy leader - you want him to survive. Lure the heavies into the forest, where Auxilias destroy them. Once this is done, move the Auxies to the flanks and run for the enemy light infantry. (While they are moving to the positions, you may overrun the routed heavies, but don't expect that Legate will hit many of them.) Then get rid of Coriolanus alone.
You may purchase pincushion with Spearmint flavour for the next battle, the
Latin Dispute, but if you don't want to waste experience, and rather lose a bit of fame, buy the third Auxilia. There's a trick how to avoid been trampled - put your Legate in the middle of the first row. Once the enemy comes closer, he'll run against them and the cavalry will suround him instead of trampling the Auxilia. But you may lose your leader, of course... Either way: put your guys on one flank, so that they don't fight both cavalry at once. After you'll get rid of them, win the hand to hand contest. Btw, it's quite a good idea to keep one Auxilia against the enemy Skirmishers. (I've lost 23 men of my new Auxilia, but I find it better to make some levels asap - mainly because MiB is ever closer -, than to purchase a pincushion unit to eat the arrows.)
There is a large area of boggy ground all around the
Etruscans At Caere map, so just run into the harsh terrain and lure the enemy heavies into it. I placed the best Auxilia on the right flank to get rid of the Skirmishers. You may also use pincushions to eat their javelins, of course. Be careful to keep the fight in the boggy ground, exactly as the briefing says: the Auxilias tend to chase the enemy and run into the open...
Gauls and Latins (the third minicampaign):
You're entering the third minicampaign with a solid force of three Auxilias and quite an experienced Legate, but you lack five pennies to make a real firework. Nevermind, lets see what we can do.
First of all, the next scenarios are quite hard, with
Men In Black been the singlemost difficult battle so far, hands down. You need to counter the enemy elite (level 17) guys. And fortunately we know how to do that. Purchase a pincushion Nobles, set them to defensive and place them right against the men in black ordered to charge them. Rest of our guys formes a column on the right side, and set them so that they maneuvre into the rough. Envelop is the best way of movement, as it takes a lots of time until they run for the enemy - and you don't want to chase the heavies in open field, do you? Once the battle starts, manually move the leader into hiding, as you don't want him to interfere; remember, you can't lose him. Then TDT the MiB at least twice, but if you'll have enough order points, make it three times. (Once your cavalrymen disengage and run a bit, you may change the formation into balanced and gain some order points, but be careful, because it's not a best idea to tinker with these settings if one or more of your men is still too close to the enemy squad.) However, once the things start to look dangerous, it is better to NOT DO anything, as you need the Nobles to withstand as long as possible and to make some damage to the enemy elite. Not before long, your horsemen will be routed, but MiB should be in a really bad shape. The last stage of this battle is going to happen in the rough terrain (don't forget to Halt your guys in there), and if you wish to pester yourself, you may even try to overrun routed enemy with your Legate.
I've seen better results than
this one, but whatever... Win is a win. (Nobles had done very little this time, normally they trample some ten men in black, but not tonight.)
I reassigned the Nobles and bought a fourth and the last auxilia for the
Gallic Scouts. I formed my units into a vertical line and rushed them into the rough, where the enemy cavalry can't harm them. Easy, isn't it?
I used the very same vertical line during the
Thirst for Gauls scenario, except for one thing - there are Peasants pincushions at the top. Keep your guys in the harsh terrain and you're golden. The left flank is covered by the Hastati, so that the enemy doesn't fire at the core squads. Pincushions should slowly move further, the rest of our guys wait in the mud.
(edited) I've bought a core Archers and a pincushion Scouts to weaken some of the
Lingering Gauls. Reason behind this decision is the amount of enemy Skirmishers that I really wanna get rid of. There are too many of those javelinmen and I don't want to see my core bleeding. Plan is as follows - 1) keep the core in SE corner, 2) ride down as many Skirms as possible, 3) profit. Quite an elaborate plan, true?
(edited)
note: I mistakingly wrote some nonsenses about the last scenario. These are fixed now. It's quite messy to play the game, write the stuff, check the savegames, etc. Sorry for the inconvenience.
The First Samnite War (the fourth minicampaign):
This is my army before the first battle of this minicampaign:

The
Conscript Revolt could be won without any pincushions, but as there are some enemy missile troops, the highlighted unit is meant to absorb the arrows and weaken the enemy light infantry. The plan is easy. Auxilia will hold the forest, Archers will support with overhead fire.
Another Archers join our ranks, and as the
Campanian Allies scenario is full of enemy Skirms, lets purchase a Militia pincushions. My plan is to hold the forest once again, to fire the arrows once again, and to let the pincushions absorb the javelins once again.
Conclude the War is a limited casualties scenario, but I still bought the Scouts to TDT the enemy javelinmen. Most of my units hold the left flank, where there is a patch of scrub an rocky terrain. The extreme right is held by Auxilia, they'll destroy the Skirms and then they'll hold the position. I need to maneuvre enemy Spearmen into the rough, so wish me good luck...
Annexation of Etruria is the final battle of this minicampaign, and it will be also my final post for today... or tonight. I bought another Archers and made a defensive scrum around the rough terrain in the SE corner. There are some javelinmen on the enemy side, but having just a mere 15 Denarii, I can't get any pincushion. Maybe my Archers cripple them before they'll get in range.
The Second Samnite War (the fifth minicampaign):
Ok, so I decided to stay for a while yet...
If you wish to
Relieve Neapolis, you must take the enemy heavies into the account. I made a defensive line in SE with my Archers in rear. Hopefully they'll weaken the enemy before the lines meet. And I also purchased a pincushion Velites against enemy javelinmen on our left flank. There's a little woody area there, just a few trees, but enough for the Velites, who, been a missile troop, won't run from this place chasing the enemy, but they'll rather sit there until they'll be out of ammo. But our main concern is the SE corner... Btw, it's not a bad idea to shuffle your Archers, so that the best ones are hidden in the corner. Oh, and buy Stronger Bows to those that may use them!
Or not, if you wish to have your last Archers already during the
Battle of Claudine Forks. I was 25 Denarii short, so I just bought bows and arrows and purchased Spearmen pincushions. I made a defensive cluster in the SW, copying the river line. One Auxilia held the right flank, the patch of rocks. Pincushion were sent forward to distract the enemy on my extreme left, where there are some light units and missile troops.
Plan for the
Battle of Lautulae is very simple - arange your squads into two defensive lines, with Auxilia in the front, then position all your men into the forest. Get a pincushion Scouts to chase down the front Skirmishers, than provoke the rest of the enemy and lure him into the forest.
Etruscan Treachery is a time limit battle, and a tight one. Purchase a pincushion Nobles to speed things up. There's a vertical line of harsh terrain on left, so try to fight there. On your right there's another little rough patch, so get one Auxilia there, destroy the Skirms and hold the position. Nobles may kill the central javelinmen and then lure the enemy into the scrub.
Ok, so let THIS be the
Final Battle for tonight... I bought the last one core squad, the Auxiliary Cavalry. I placed them against the Samnites' light infantry, so that the enemy has lesser jaeger units. The rest of my squads made a defensive perimeter in a forest, Auxilia in front, Archers back. I plan to TDT as many light units as possible, starting in the centre and making my way to the left. Then I'll run the Cavalry upwards and return back to seive routed enemy for some free experiences. The Auxilias need to hold the line, but as there lots of skirmishers, I'll buy yet another squad, some pincushion to eat the javelins.