I’m not an Affiliate Webmaster (yet) but i’d imagine that there’d be no one thing that would set out any particular Affiliate programs above the others.
You’d have to measure CPA or Rev Share % vrs the quality of the pokerroom/casino/bingo site.
No use having a sky high rev share if users only visit once and find that the casino sucks lemons.
My unqualified opinion would be to suggest you try some sites out yourself and choose from which sites you think other people would find easy to use and good. great stinking huge deposit bonus would help too.