If we are talking about risks here then I will just to used martingale on which Im alway using. Im a NBA enthusiast for years now and my knowledge here help me in some of my bets. I losed sometimes but overall I have a great winning stats.
It's impossible you will lose 5 or let's say 10 times in a row on your favorite sports so martingale will be an effective strategy (just make sure you care for the odds ; parlays will work too). If on the case that a gambler losed 10 times in a row , then stopped doing gambling lol.
I agree with you on only betting on sports and matches that you are comfortable with, and have some knowledge about the game and the teams. There is not point in betting in a lot of matches. You better do some solid research and bet on on game or a small number of games in a day.
As for martingale, I do believe it might work in sports betting, if you can really find good odds, otherwise I'm not sure it will work. I don't think it's that easy to win at odds higher than 2, and you will need a large bankroll to use martingale with odds bellow 2. So even just losing 4 or 5 times in a row, you will be making a very large bet, that you shouldn't probably be making. I think in sports betting is all about bankroll management, so that you can keep betting for a long time. By doing this, even if you get unlucky in a few games, you will still come out with profit on the long run.