Best regular game at quarters is 8/5 BP at 99.17.
Actual best game there is Dreamcard 8/5 BP at 99.27, but you're locked in to a minimum of $7.50 per hand (three hands of quarters at 10 per hand), which might be beyond your variance tolerance if you're just trying to grind to 50 tier credits.
Tabbycat is correct that you can ruin good Harrah's offers elsewhere by mixing in some low level play at Rincon. So if your average day at other Harrah's properties is 1000 tier credits, you don't want to mix in some 50 credit days. But if you're typically only doing 100 credits a day, you're not going to lose anything.