To my knowledge, playing in gambling is just pure luck and there is no winning strategy. and does it have to be big to win big bets too?
There is some common knowledge about how to win the contest (at least in theory).
1. For multiplier, go for at least 5,000x max-win because you can't win multiplier contest if you play 500x or 1,000x max-win games.
2. For max hit, you can play medium volatility with higher bet, $1 for example since you don't need a massive multiplier.
3. For bonus buy, go for minimum buy, $10 previously.
That's about it, and you need decent bankroll if you aim for #1. If only for last place, or for fun, I deposit only ~$80.