Well if you are low on resources in Leyte means your force composition is not suitable or you have been taking heavy losses earlier. My suggestion as below which I found it very helpful.
Infantry
Infantry don't really need transport except for that blue truck that can cross water those are awesome
Entrench enemy always hit with engineer first as engineers are cheaper to replace. If engineer is out of range use heavy infantry to tank but do not attack and place engineer behind and swap place next turn.
Marine vs infantry always a tough choice as marine does better in some scenario but don't over purchase marine as infantry is far cheaper
Tanks and armor
Facing Japanese you don't really need anti tank as their tank is below specs so don't over purchase armor as they are expensive to replace
Light tanks perform great job in supply cutting so don't buy too many heavies
Plane
These are very expensive to replace so beware of the losses taken during earlier campaign.
Ships
Don't buy to many fancy BB as they are slow and sometimes I find CA and DD far better and far cheaper
Basically try not to engage enemy head on as that would really hurt your resources. Game design is awesome so you have to learn the basic engagement which will really help you. Flanking is great, cutting of army from supply is good if they are very heavily entrench
All unit have their use and purpose so you just need to learn them
, I am at the final campaign for both US and Japan on 3rd difficulty. And I decided to do vice admiral which is tough hehehe
Hope this help
