I have played on fanduel for about 4 years now (NFL only). Usually play 5-7 tournaments each week spending $75-$125 a week. The most I have ever won in a single tournament was $250. I finished 586th out of 114942, this was last year in a $25 buy in tourney.
Some shady stuff definitely happens. Good example was last night when I was looking through the live rankings. The first place guy had 7 entries and every one of them was the same. Shady to me that not only does he have 7 of the same entries, those 7 entries just happened to be the top line up. No real way to keep tabs on every lineup in a contest with over 100,000 entries. Best advice I could give is to play the 50/50's, they wont pay as much but your win percentage will be much better than the scam bigger contests.
Someday the fantasy sites will get sued for their false advertising and the scams they are running, until then I will continue playing them realizing that I wont ever become rich doing it but it's fun trying.