Joining bounty is a very risky thing to do knowing that there are no guarantees that you will get to earn the profit you want from the very first place and you might even get nothing if you are too undortunate. It is very important to choose a bounty smartly so that your time wouldn't be wasted on nonsense bounties.
Choose a project where you can see some real, most of the ICO extends promotions and some just walk away after launching it, the key is to be updated and keep studying it if it's worth joining, investment of time and effort should be paid off.