Fastest way to far Merits?

I'm trying to buy for my Psychic/Mental blaster, the Blaster's Wrath Set; so I'll need 600 Merits to get the full set. Also, I'd like to get some of the Set IO recipes.What's the fastest and most efficient way to farm Merits to get to 600?And what's the best power to slot this set in? Should I do Psychic Wail, Psychic Shockwave, Psychic Scream, Mental Blast, or Telekinetic Blast? via /r/Cityofheroes http://bit.ly/2EM4mGe