Leves is by far the fastest way to lvl. If you turn in the required item as HQ you can get double the exp from the leve, so you can get to 50 with in less than an hr if you have the required items in HQ and do the aprorat lvl leves. Im not sure for 50-60 on speed lvls as i havnt started lvling mine to 60 yet. I would asume itd be leves and the daily collectible turn-ins you can do that would get lvls.