Put the time in with gambling and you'll win long-term, it's as simple as that.
With that said people often don't want to put that time in, and the less time you put in, the more of a factor luck will be.
It's not dissimilar to how you can put a lot of time into looking for ante-post bets which are overpriced and you'll eventually win long-term because you're beating the market.
As for specifically advertised "risk-free" bets, if you've got enough time and are well organised, I don't doubt it you can make a modest but consistent profit every month. Depends how you see gambling. Is it betting for profit, or is it betting for the thrill? The latter attitude is why bookies will always win.