For me, the gems that I choose are:
1. Managed by famous BM
2. Bounty funds via escrow
3. The bounty allocation is reasonable, not too big and not too small.
Then just do a little research on the project to be followed.
This can be one of the main references for bounty hunters to choose to join the bounty project, which if based on previous events there are too many events that the results and work are not comparable. And the last addition from me is that the bounty manager at least has positive feedback.