Well, having people to play with is quite fun, makes it more interesting. There's like three main things do to. 1) PVP 2)Raiding or Dungeons 3)Grinding your character's skills and level.
PvP and the Raids or Dungeons are gonna be better since you'll have people to play with and won't need to waste like 20 minutes looking for a party just to have a moody tank leave on you. The rewards for PvP are epic, since you can get epic gear, or get another race's mount without having to be at Exalted reputation status for like Darnauss to get the Tiger mount. I'm sure you'll get into it, like everyone else.
What class and race will depend on what you like. It's usualy pretty fun to try them all. I'm a level 60 Dwarf Paladin :>, but I also got a NE Druid, Blood Elf Warlock, and Dwarf Death Knight.
If your more of a straight forward damage kinda dude, I'd say try a Warrior, but if you like being smart about things and stuff, I'd say Mage or Paladin. Also, grinding is your friend. ;D