Playing playing playing playing...if you don't wanna resarch all modules (but sometimes it's recommended) you can skip something of Panzer III (like "Stubby cannon" or radio).About Panzer IV I advice to you to resarch all modules (tracks, turret, engine, gun) except radio (you aren't a scout tank so you'll not go too far from your mates).Other tanks like all VK prototypes I don't know it very well, but more high it's the tier, more times you've got to resarch all modules.Moreover, if you have a Premium Account you can get the Panther and Panther II easly, but without it it's impossible because the manteinance costs starts to be too high at tier VI (for heavy tanks) and VII (for medium tanks).