1) Asura. Most servers are sadly half dead so it gets really hard to do catch up content if you are a new player
2) The best way is to get a LS and ask around to people. You can get it from a LS NPC near the town entrance. Also a) Get trusts as soon you can b) Learn what RoE is and follow the Tutorial RoE c) Get an unity d) Touch every crystal and book (Survival Guide) you run into, you'll be able to warp to them
3) Doesn't really matter for leveling content these days, anything goes. Leveling is quite fast so don't be afraid to experiment. For end game, like most MMORPG, Tanks healer and supports (GEO, COR) are the most requested class since everyone plays DD.
4) Doesn't matter.