First of all, welcome back.

Get a exp pt on abyssea and get enough cruor (abyssea currency) to get all the maps, KI's and abyssites from entrance npc's (esp lunar abyssite for your first atma infusion). With maps on yar hand and cruor on the other, wiki aby maps and put snk invis and rr (some mobs are true hear sadly but there are few) and walk all your way to the fluxes and open them and mark it on your map. Will make your aby experience a lot more easier.

You will hear a lot of different ways to cap your skills and many of them will be good. My humble opinion about skill ups is you must do it on abyssea and there you have many options, get someone who can heal you and use your skill up food or even get /dnc if you don't have atmas at the moment, if you do get some regen atmas and hit crabs or w/e mob you feel comfortable with. If you think you are dying too fast you will need to change mob type or get a healer pal. Shadow zones are not longer good to skill imo, but always ppl will differ.

About atmas and triggering system I could type it for ya but, honestly, it will be easier to get into wikipedia (or bgwiki) and search "stagger" and you'll have a good explanation about it, not everyone knows em, normally ppl who are used to stagger don't tell you cus prolly they dun want to get their fingers tired, never the less it is rude. So when that happens, wiki ftw.

If you want atmas you will need to check out shouts that aren't for leveling, unfortunately, many ppl are interested in VoidWatch atm so atma shouts or farm shouts are few, in those cases get your friends together and wiki what atma you are looking for and how to defeat the monster. Just find someone with abyssite of discernment to know which triggers you must use. At first it is a pain but i'm sure there will be someone around happy to help ya.

Abyssea system can be overwhelming at first but ppl catch up pretty fast. And then start to enjoy it. Just as a reminder, there is a world outside abyssea lol.

I'll be happy to help you more so feel free to ask. but atm i know it has been a lot of info lol.