I saw DK doing their generic "up to $,1000 deposit bonus" promo earlier this week. Believe the fine print said you have to earn your full bonus w/in 45 days of initial deposit & the playthrough criteria is ridiculous, so you better like betting on UFC & Korean baseball A LOT.
Seeing FD & BetMGM both offering a risk-free bet of up to $500. "Refund" your bet in site credit if you lose. If you're patient enough to fish around Google, you can probably find some decent referral codes from sites like Action Network, etc.
All that said... who's ready for some 4-max poker at Ameristar?!?!?