Queue for Dungeons.
Do the Low Level Roulette.
Do each Guildhest at least once, also do the Guildhest Roulette, may not seem like much but a Guildhest is only a couple of minutes long anyway.
Do FATEs.
Do what Challenge Log you can.
Do Levequests.

Dungeons are best IMO. Especially if you can score a friend to Queue with who is a Tank or Healer (Or both if you have enough friends)