The per player value of casino players is definitely higher – but they are a fickle lot and jump from casino to casino a lot.
Poker and bingo players spend less money, but they settle into a community and you need to stick with it for some time to establish a player base.
In the long run I prefer bingo and poker because it is stable, bread and butter income. It grows every month and I can see myself promoting these 5 years from now with a very nice income.
They are much more likely to support you while you quit working on promoting them.
That is my opinion only, and time will prove me right or wrong.
As a novice, I would promote all three sectors. It is a bit more difficult to start out in the casino business nowadays. And it, too, takes time to develop.