I suggest a 10-game limit to even appear on the standings. Otherwise, we have the chance to see the #1 spot taken by someone that played one game against the best player and happened to win.
As for the 30 game limit with ELO, I see no reason to have it impact the prizing rule. "Simply getting a lucky streak of wins" is actually a bigger problem for players that have already been in the league for a while. They can start their lucky streak of wins at a higher spot, such as a 1550 rating, instead of the 1500 rating new players start with. And statistically, good players finish higher in the standings as they play more games. KRACH with a 30 game limit fixes any lucky streak of wins problem, of course.