- how big should your fleet be consumption-wise ? Is 7,4 per day way too much ? The thing is that i recently took a 300k bounty mission to kill a ludic path orbital base and i was barely able to win, so i don't see how i'm supposed to play with a tinnier fleet.
Well, dude, there are ways to make your life easier. First of all, there are personnel skill to decrease maintenance and efficiency overhaul hullmod doing the same. Also, do not forget to salvage a couple times debris field after each large battle. Having salvaging skills and a couple of salvage rigs would give you ability to maintain much larger fleet and even sell the supplies. Also, check if you waste supplies to nowhere. Some ships are just to hungry - get rid of them, some ships have D-mods that increase maintenance - restore them (usually cheaper to buy new). Having crew/cargo/fuel over capacity will cause supply consumption penalty, so do not have more than limit. Also, there are such thing as commission to decrease monthly credit loss. Many minuses, tho'.
- i didn't started a colony yet : can this help me get supplies cheaper of more money, allowing me to play with such a big fleet ?
Short answer - yes. But it takes a lot of time and money before it is. Initial stage is very expensive and require a lot of babysitting.
- are the repairs you "buy" at a friendly planet or orbital station (repair ships for X supplies) cheaper that having your ships repair themselves on their own ?
Didn't check, but I believe it is.
P.S. Simple screens with your fleet and detailed maintenance (hover the value and press F1 to expand maintenance list) would help to determine a problem.
P.P.S. Legions are hungry expensive ships. They are great, but not for early game stages.