Congratulations.

Now you get to assemble your teams.
I'd recommend a diverse mix.

A PvE team, for heroics.
A PvP team, for battlegrounds and/or arena.
A melee team if you don't have one.

You can focus on one, if that is more fun than the others.
Or you can play any team, until its rested expires, then switch to another.

You have a lot of combinations to experiment with.
Should be lots of fun!