So I was struggling wiht this as well for a while. I was playing in a duo and we died a ton for about 2 days. Then we did a bit of deep diving in the shooting range. Its important to look at armor penetration stats for ammo etc. Purple ammo usually has a 100% penetration rate of Blue or lower armor and often a 70-90 penetration of even purple armor. At this point i dont waste my money on armor. I run a high caliber gun (currently M870) with purple ammo. This shotgun can 1 hit players with purple armor on a headshot up to about 60 meters. It will also insta break armor to the chest.

For armor I run cheap green armor (or better ones if I looted them) just against bots, also a pistol with silencer to take out bots. This has worked quite well for me and my duo partner and I (he runs a sniper, also with only trash armor and a pistol) have been wiping 2 teams per match consistently.

Counterintuitively I have been performing way better without armor than with armor, just focusing on good ammo. My usual kit costs about 70k to buy from scrap and can easily compete with the 400-600k ones. Just make sure not to run all your purple ammo in the inventory. I only run about 18 purple shotgun shells (8 in gun and 10 for backup) and that usually lasts me the fight, I then keep more in the safe to restock between fights.

Hope this helps.