Use cover, slow-mo, and the leaning ability.
Stay away from fuseboxes.
Once you have the G2A2, try to keep it as long as you can. I kept it until around interval 9. At that point I had the Type 7 with about 30 shots, the Repeating Cannon with around 35 shots, and the MOD-3 with 12 rockts. That will last you for the rest of the game because you are given the RPL and the pistol once you get to Interval 10
If you come across a power weapon, save it for Mech/Heavy Armor.
Shouldn't be that difficult.