Need priest advice please. Pic related is my setup right now and I'm not sure where to go from here.

I can keep going down disc and get some more mana and raw stats. Other than reflective shield though (and idk how good it is) I'm not sure if this is helping much for continued leveling. But it'll probably help for dungeons quite a bit.
Alternatively I can start creeping into shadow for improved SWP and shadow focus, then grab mind flay.

Finally I can just wait until 35 and then respec shadow, since I can get shadowform I think. But then I probably can't do dungeons (and dungeons blow ass on shadow)