Gonna start sperging a bit about gambling but these two moves are enormous red flags for problem and bad gamblers.
The first one, betting on Japanese basketball, is a big red flag that someone is a problem gambler. Betting on football games is one thing, being an American, Ralph probably has a decent idea of the teams and their strengths and weaknesses so he wouldn't be at too much of a disadvantage, but betting on Japanese basketball is completely different. He's completely at the mercy of the bookies, has no idea if a line is good or not, he'll have no idea if a bet is decent value. It's a big sign that someone is addicted to gambling when they start betting on incredibly obscure sports.
The 2nd one, him betting 150 to make 50, just highlights how fucking dumb Ralph is, bookies love these bets, the sort of bets that seem like sure things so the Ralphs of the world have to put up 150 to make 50. They're not worried about dropping 50 here and there, they know that if they keep Ralph betting these long enough eventually things we'll break they're way and they'll clean the ralphamale out.