Betting on E-Sports is much the same as betting on traditional sports like the NFL, NBA, or MLB, and this is reflected in the betting markets on DraftKings Sportsbook. For example, right now users can wager on both LoL Champions: Korea and Counter-Stike: GO Blast Premier, and we can see the sort of bets you can place.
So, while esports in only 100% legal in Nevada and New Jersey, there are states in which you can access regulated esports betting: These states include Arkansas, Iowa, Mississippi, Illinois, New York, Pennsylvania, Rhode Island, Washington DC, Oregon, Montana, New Mexico, and Delaware.