These chances don't change - you can get higher quality items as you level up, meaning you get the chance at better pre/suffixes, but the chance to get rare/unique/set is always the same.The items you receive will be from most common, to most rare: Magic Items, Rare, Sets, Uniques. Set and Unique Items are extremely rare. The chance for Uniques is 1 in 5,000 and 1 in 2,000 for Sets. The chance for Rares is 1 in 10. The level of quality of the items will be from most common to, most rare: Normal, Exceptional, Elite. The chance for Exceptional items is 1 in 11 (or 9 in 100) and the chance for Elite items is 1 in 30 (or 33 in 1,000). You will mostly get Magic items which may or may not be worth anything to you (hence Gambling).