I don't have a bankroll at the moment but I think it's not crazy for people who play poker or sports betting to get 10% a month. Winners I mean. Obviously more than 90% are losers.
After writing this I was curious to see what the AI was saying and it said no, for winners half of that, or even less, would be more realistic.
Poker
Level of Play Realistic Monthly ROI on Bankroll Notes
Casual/Low Stakes Grinder 1%–5% Soft games help, but volume is key. Swings can be brutal.
Strong/Semi-Pro 3%–8% If you table-select and put in solid volume.
Elite/Pro 5%–10% (some months) Very good players can hit 10%+ occasionally, but not consistently. Variance matters.
Tournaments All over the place Huge swings: you might lose for months, then hit a big score. ROI is high, but consistency is low.
Sports Betting
Type of Bettor Realistic Monthly ROI on Bankroll Notes
Recreational Negative to 1% Most bettors lose over time.
Semi/Sharp 1%–3% Requires discipline, tracking, line shopping.
Pro/Sharp 2%–5% (on turnover) Sustainable, but you’ll have down months.
Syndicates/ High Volume Pros 1%–2% monthly on bankroll Massive volume, small edge per bet, and excellent market timing.