Since you're also new* i'd suggest guy in my Sig below, but many top sellers are genuine. I went first in transactions.
There's alot to be hesitant about buying + selling. Imo and past trades usually trying to get the top dollar never really works out, leave it to the big dogs to make their cut...
My thread buying Phat is here: http://www.sythe.org/runescape-item-purchases/1523610-phat.html
Looking to buy Gold logically equiv to Phat price, which ever comes first.
Primary method : Bank Transfer