No worries! I have slowly turned from someone who thinks a moderate amount about gear to someone who's gone totally crazy with it.
- Unless you are dying very rarely, I think Comeback is a fantastic ability for a Carbon cause it gives you increased Ink saver, ink saver sub, run speed, swim speed, and special charge up for 20 seconds after you respawn.
- Ink resistance, definitely! The Red High Tops are likely to give you Swim speed plus your ink resistance, which is a great combo, especially for rainmaker.
- Swim speed is always good, especially paired with Ink Resistance. If you like sneaking about it's especially nice cause if there's not much of your ink around and you need to get somewhere quickly, you can swim and jump in tiny bits of your ink in a sea of the enemies. I don't think I explained that very well but.... o_O
- Ink Saver Sub is also amazing for Carbons. If you pair it even two sub slots of it with Comeback, you can throw three burst bombs while Comeback is in effect which makes a big difference at a small cost gear wise.
- Damage up, of course. >=)
Depending on the mode too, I mean if it's splat zones some extra Ink Recovery and Ink Saver Sub might be a good idea.
Also, (Just cause you say you're not to knowledgable about gear), each brand has a different ability that it has a higher and lower change of getting. As a general rule, I look for Firefin, Krak-On, Tentatek and Squidforce cause they're all brands that are likely to roll the abilities I listed. You can see a breadown of them below
https://www.reddit.com/r/splatoon/comments/38nuy2/each_clothing_brand_has_a_higher_chance_to_get_a/
xD