There are tons of beginner build guides here Beginner build guides Compendium (for AoM + FG expansions) all of them uses faction gear, monster infrequent, guaranteed drops, and common epic items (blue) 
Try to decide what play style you would enjoy most and narrow down the list of possible builds. Like do you enjoy melee, ranged, caster, pets? AoE or single target? Tanking or kiting?
Otherwise, with the advent of monster totems, farming legendariers have never been easier. Even a quite suboptimal build can clear monster totems in ultimate pretty fast. It might not be as high return of legenderies / time as say SR 65-66 in ultimate, but it will at least provide something.