Everything they only have is free to enter but they do always pitch you on offers constantly when playing. But that's done on their site and no purchase is ever required to enter.
I normally just play them when I'm waiting on someone. I used to play freecell for something do while I'm waiting for some process to run or a project is on waiting for replies. But I thought might as well be playing something and earn a remote chance of winning something.
In the 3 or 4 odd years I've been playing, I've gotten a check for 10 bucks in the mail and 2 Amazon gift cards for 10 bucks each. Nothing special but more than I'd earn playing some card game on my pc. I bought one cheap thing one time early on, but the order process is slow & shipping cost was higher than a lot of other places online.