Now, leveling up scales. Going from Level 0 t0 Level 1 requires 5 items, as does going from Level 1 to Level 2. At Level 2, it rises; Level 2 to Level 3 requires 10 items.
Unfortunately, when you level up, you get an randomly selected item (from a pool of about 6 items):
Right now, to me at least, I have not seen any conclusive evidence that makes me think this is worthwhile. With that said, you can get some good rewards from mastering the higher levels (6+). Whether this is worth it to you, you will have to decide that for yourself.
Maybe the rewards will be even better for higher levels, we will have to wait and see!
However, if you do send a gift to your mafia members by responding to their Mafia Wars Crime Spree request, you can pick 100 XP, 50 energy, 0r 10 stamina as a reward. I guess it is truly better to give than receive!
Oh, and here is a free rewards point link: