Keep parlaying by betting just $1, it wouldn't really make me a millionaire but the amount is so much bigger than betting on one match and then just being hopeful to win. The winning ratio depends on how many matches are in the multi-bet but having just about 10 I think is not so impossible. I'm sure I'm not the only one who are doing this but many of us who play in sports.
To be a millionaire with $1 bet, you need a combine odds of x1,000,000,00... I don't know if there are sportsbook that allow that kind of odds, probably there's a limit, so you need to increase your bet if you really want to earn that million once you get luck. Make it $10, it would be easier though in general it's hard.