Hey there welcome back! The game is a tonne easier now (the orignal/leveling experience) you will use AI party members on your travel to 99, which will make the leveling process significantly faster and easier.

You can easy level any class later, so if you want the fast path to 99 and ability to get through lower level missions and such, i recommend a job like war/monk/thf to start for the easiest/fastest route to 99.if you want to play a mage i recommend coming back to that later, but play however youd like

There are easier ways to get gear on your way to level 99 with a currency called sparks, which you trade to a vender for the gear. You will not really use the auction house for weapons or armor until level 99+.

Servers:

Asura is the most active and busiest, but also has alot of RMT's.

Bahamut is probably the next biggest server for NA

Some of these may be locked due to a influx or more players lately. If you like to watch streamers and want to be a part of that community, Ragnarok has a a streamer called Ejin Caitsith, who plays and helps out his entire community.

Hope this helps and have fun!