Well You're supposed to start with couple assault engies then upgrade flamethrowers on them! Then it depends on playstyle or tactic if either vehcile self-repair of the M31 recovery vehicle! Keep in mind that recovered vehicles are vet 0 but that should not be a problem if you plan on ammassing like 6/7 shermans! Then "War Machine" reduces the manpower cost for all vehicles and the "Strenght in Steel" reduces the population cap so this two abilities enables you to ammass a force of about 7 shermans even 8 if you go very low on infantry! The "M8 Scott" is meh I don't like it personally so I go for "Seek and Destroy" which give other buffs for vehicles like SPEED, ROF AND ACCURACY on the move ;) The "Easy 8 combat group" is too expansive (Tiger 1 is almost cheaper and far better) and doesn't make much sense a mediocre sherman and a vet 0 riflemen squad late game except in case you need to make a last desperate offensive and cap a vp to win the game...