It depends on what your goals are.

Have you finished all of the storyline so far (up to Ramuh)?
With the patch tonight there is the introduction of the 5th beast tribe and there is supposed to be a special quest when you finish all 5. Since you are limited to 6 quests per day though, this will only keep you so busy each day.
If you want to get further in coil or the extremes, get your ilvl up into the 90s. You can do this with soldiery gear or Syrcus Tower drops. You can also try doing hunts to collect seals to upgrade the soldiery gear.
Getting your atma and then doing the books is a large time sink but will eventually get your relic weapon up to lvl 100 .. or 110 if you do Novus.
If you are feeling at a plateau with your current class, try leveling a different one.
The DoH and DoL classes are great time sinks and can make you a lot of money, but don't do them if you find them boring.