For a $25 buy-in I'd go with a $5 bounty
For $50, go for $10 bounty
It's good when the bounty is a somewhat significant percentage of the buy-in so players that win a bounty or
two get a reasonable amount of their buy-in back
We play with a bounty and it’s great for spreading a little love around for the non winners. It’s amazing that you can lose money but if you take home a bounty you are in the hole and still feel good.