Upgrade to 16gb of ram. Make sure it's the same ram that's in your PC now. You don't want different speeds of ram in your rig.

Next.. use nvidia GeForce experience to optimize your games.

I have a 2080ti and spent about 4k on my PC, and most shooters I don't even use max settings. You want more frames when it comes to those. Please tell me you have better than a 60hz monitor for COD

I am definitely getting 32GB, I've been wanting to upgrade since I got it.
My current monitor is just garbage.. it's old. I am also buying 2 new monitors to replace my 27" monitor and 50" LCD TV lol.

I have bought a bunch of older titles, plus I've had games I bought and was never able to play on my old system.

My current list is:
Borderlands 2
Borderlands 3
Call of duty: Moderwarfare 3
Call of Duty: Black Ops 2
Diablo 3
Fallout: New Vegas
Portal

I think I may have 1 or 2 more, but I'll mainly be playing Runescape 3, OSRS and boderlands. Maybe a few rounds of CoD a week.

Make sure the monitors you get are atleast 144hz and 1ms, makes a huge difference.