The real key to winning is actually simple, just pick the right team to bet on. No fancy betting strategy will save you if your picks are trash.
Honestly, flat betting is even better. Slow, steady, and way less stressful. ( you should try it )
You are very correct that the strategy can not work and he may want to use small amount of money for it but the martingale will make the money huge. He will realize that after losing that the money he finally used for it is huge. Bit you are nit right that if someone wants to win while gambling is actually simple, it is not simple at all and it requires luck. I am my conclusion that no one should look for winning in gambling but if they do, it is not guaranteed.