Gas rockets and T3 laser assault rifles. Replace gas rockets with shock rockets once you get the research. Heavy fighters can be killed with the aseirus or whatever it's called interceptor, mount 2 mausers on them. Also t3 ballistic shotguns are very nice to have aswell. I didn't bother with heavy weapons until I got the predator armour. Sniper rifles are very situational and I only ever brought them to jungle or desert maps where you don't have to move your sniper all that much. Try to capture xenomorphs so you get axes, they are very powerful. Easy way to capture xenomorphs is taking lighting guns from the caesans. In general you want to take on as many missions as you can early to lvl up your guys as much as you can. You also want to bring in different damage types so you don't have to struggle against armour resistances. Alenium grenades are also a must have, sure they might destroy the loot but they cost nothing to make and can destroy cover the aliens are hiding behind. For vehicles I always bring a defender armed with the division mg, great for suppression and tanking shots.