The system seems a bit odd at first, but just remember the saying "need before greed". If everyone chooses Greed then whoever rolls highest gets it. Choosing Need just tries to swipe it straight away. Note for items that you don't need, you should click the X on the top right of the pop-up window to pass altogether.
Btw, for those unfamiliar with MMOs I would strongly advise against trying a hybrid AC (i.e. investing points in two or even all three talent trees), lest you end up gimping yourself. While some hybrid builds may be effective if spec'd right and played well, you'll find a "pure" build will serve you far better until you learn the ropes.