Here is a list of a few of the csgo betting sites where you can try your luck on winning, or losing skins. Please note that most of these sites take a percentage of each pot, usually 5%, and that there is always the chance that winnings might be lost into the ether for a myriad of reasons, so use these at your own risk.
The most popular is CSGOJackpot. Pots can easily soar into thousands of dollars. There are many cases of pot sharking, especially when big name streams are online. I would suggest making your wall comments private, there are a lot of users looking to obtain free stuff. On a side note, there are two different skins for the website.
They limit deposits to 60 dollars per item that ultimately creates a smaller pot size. I would suggest people who are new to the scene, or just feel like throwing a few cheap skins around to use this site.
Many high-profile streamers like to use CS:GO shuffle, it is one of the few sites that allows for players to interact with each other by using the chat function.
What was once known as ItemJackpot has come back as Crimson.GG. Its game play seems to be quite similar to the old version of ItemJackpot with a timer running rather than waiting for a particular number of skins to be deposited.