As melrodys said, expercience boosters( expb's ), skill point boosters (spb's), platinum blessed iris ( pbi ) and platinum super skill pill ( pssp) are the best items to sell, however you can also sell heaven stones (hs), lucky smelting stones (lss) and runes of protection ( rop) for a decent price. As for sp, let's say from lvl8 to lvl17-20 you can farm on Sasquatches, then you should try prokion, but i've heard it's no longer gd, so maybe after lvl20 you should try elder drakes until like lvl30? And any event announced by Aeria can only be decided by the GM's ( when,where, how, etc)
P.s: you don't need to use spb's from lvl8-30, because the sp ration+exp lock is already enough to give you decent amount of sp.