buy the gun, then hull and then turret

the hull is very fast, has some armour protection and suspension hull aim

all the starter Tier 8 turrets are awful for new players but you have to buy something to progress so just pick whatever (if you really want a turret that works you can get the Cockerill 3105 turret from the blueprint shop as it is cheap to craft)

the gun is more powerful than the 84mm although with only slightly more APDS pen, you also get a HEAT shell for combating with tanks with stronger armour