You cant bet with BET tokens
If you can not bet with BET tokens and win EOS or BTC and if you can not sell them for cryptocurrency or FIAT money, then they are currently worthless!
How do you determine how many BET tokens a player gets?
Well worthless to you apparently, BUT it's true value will be decided by the market when BET tokens will be listed.
But FYI, the only use of a BET tokens is receiving part of the house edge (which is in EOS and BTC). The market will decide how much a BET will be worth when it's listed.