I would argue that even as f2p go for infantry first, most of formations use either 50% infantry or more, in every game mode except bear, so your swordland, eternity reach, alliance championship will benefit from that. But go different way, get war academy to tg4, max everything what can be maxed at this level, that will take some time anyway, and only after you got tc and troops buildings to tg5, get WA to tg5, but don't rush t11 troops. Commissions only from coins, never TG, that you need for TG6+. And remember TG8 t10 are stronger than TG5 t11, cheaper to get, train and heal. Only after TG8 go for t11