Hey, like you i also returned to the game recently after a long break. Last time i played was the high five chronicle. Im currently on Giran server for about 2-3 months now.
Its crazy how much the game has changed. The whole "classic" is very different to what you probably would expect. I was talking with high rank/ lvl players and every single one told me they have 3-4 parties in different locations for example Cruma tower/ catacombs farming adena to build up their mains. This took me by surprise so i went there and behold it was true, i couldn't find a spot to level.
Classes I'm not too sure about, it seems titans, duelist, summoners/ mages are all doing decent. Personally i chose duelist.
When making a new character i recommend to create other characters such as buffers so you can level all of them at the same time. Unfortunately this game has become a multi box fiesta.
Also you should know you will probably have a very hard time as a free to play player unless you're willing to invest a lot of time and money into your character.
btw Classic is my favorite version of the game, ive tried both live and aden servers and it just doesnt feel the same level of fun to me. I just wish there was more newbie friendly content, instances and better drop rates.