For gambling 'bet' is just about the best string one could use for a new gTLD, gambling related domains have good historical sales.
Premiums are around $3,750 reg and renewal - non-premium around $15 reg and renewal.
I checked random popular betting terms and I found most are premium. You can find some which are not on the top shelf but have aftermarket potential.
No surprise to see some like alpha.bet and free.bet not available for registration.
It's likely to be favored by Chinese investors as they have insatiable appetite for gambling.