Slitherine

Hi, Am I missing in the rules the path to take to get unit upgrades like Marian legions for Rome and general upgrades for others like Egypt? Do you need a certain number of training grounds or barracks?

first, you must be at third civilisation level for them to apear. as in, you must be empire/confederacy
then you might get a decission to reform a type of your soldiers. each type requires different buildings. iirc 3 baracks or 3 furnaces is for upgrading normal infantry. number of them doesnt seem to raise probability of getting the event.
marian reforms are time based. you just have to wait.
edit: you also need to have 2 (for lesser ones) or 3 provinces (for actually usefull things like heavy infantry) to be able to enact them.
chariots, elephants, cataphracts cannot be upgraded