This is one of several guides out there to give you a general idea on what to do: http://www.ffxivrealm.com/guides/monk-dps-guide-v2.14/
Of course, this is more for MNK, but you will be unlocking that at 30 if you keep going on the same path. Early on, just remember your positioning as much as you can, behind, flank, etc. As you progress and start opening up more abilities start learning the full rotations that are available to you from that guide. Another thing, level up LNC/DRG to 34 for the cross class ability Blood for Blood, that combined with Internal Release becomes quite potent in end game.
As for other cross class abilities, the guide does describe some, I myself use Fracture, Invigorate (very useful later on), Foresight and I think one other one. Another thing to always remember, keep DOTs up, it goes down, put it back up. Main ones you can use are Demolish, Touch of Death and Fracture if available. If you go to re-apply them early, and they were applied with a buff up (ie: Internal release) and you no longer have a buff, it won't overwrite as the other is stronger. So you would have to wait until it has worn off.
Lastly, abilities such as howling fists are not on the same cooldown as let's say Twin Snakes. So you can start your rotation, immediately trigger howling fists and go straight into your following rotation atk without losing a beat. The same goes Internal release, Blood for Blood, etc. Use them in between rotation atks so you're not wasting time.
Gear wise, there's also lots of threads out there if you google, general consensus is STR/Crit/Acc/Determination/Skillspeed. Of course, as you approach endgame, this becomes debated by many. Some swear by Crit over Determination, others vice versa. Some like the returns of skillspeed if you can cap it at 490 I believe it is. Then of course for Coil Turn 4-5 you need approx 480 acc, so you have to sacrifice certain pieces to reach that accuracy. Again though, several pages out there debating these things.
As you approach 50, if you're fighting a single mob that doesn't move too much (meaning you're constantly attacking and doing your rotation without interruptions), you SHOULD be running out of TP. If you're not, then something is missing and you're doing things too slow. Anyhow, I'm a stop going now, but ya..google..guides, plenty of em.
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