I haven’t consulted WordTracker or Keyword Discovery on this stuff for ages, but I would imagine the most obvious phrases are the most competitive:
online casino
bingo
online bingo
online poker
internet poker
etc, etc.
Personally, these are ‘nirvana phrases’ as far as my own SEO strategies go. I don’t care if I never get there, it’s just something to aspire to.
My own approach is to target phrases that will make me money today. In sports betting that may be as simple and immediate as:
tottenham v arsenal odds
or as long term as
superbowl XLII betting
All the rest is just gravy.