Optimizing gear is one of the hardest things in the game, since it already comes from personal preference, and the sub abilities are random. I would just experiment to see what abilities you like, most of your weapons are greatly assisted by swim speed, ink resist, and possibly special charge. Many of us can't tell you more, especially now, since this patch has changed a lot, I don't know if you need cold blooded as a carbon anymore.
Basically just experiment, and as you get better you'll develop preferences based upon your own gear, or from what your opponent is using. Like personally I know some e-liters disagree with me now, but after this patch I run only 2 damage up mains. That's what I decided my optimization was after testing it out.