If you want the 'standard' classless experience, I suggest you start on the Area 52 realm, where you get through TBC content and don't have to worry about too many mechanics.
However, the current 'seasonal' realm is experimenting with several new things that are very interesting, such as rewarding players for playing out recommended builds, challenge modes or even as the original WoW classes. This realm goes through Classic content. This realm is usually the most active/populated, so if you're hoping for people in-game to help you out too, I recommend going there.
I wouldn't recommend going straight into PvP until you have familiarized yourself with the system, as it's heavily meta-build ruled, but do know they have a nice risk/reward system if you're interested.
If you have particular questions, I can try to answer them - And hopefully others will too.