Recently i took part in couple of bounty campaigns,and i though i can earn some decent amount through it...but it was a total waste...i took part in targetcoin and coss ico campaign and after 2-3 months i recieved the bounty which is worth only about 8 USD including both

it was just total waste of effort and time
It really depends on the budget of the project.
No, the most important thing is, it's depends from the project, is it still active after ICO ended? And will the dev keep their promise to always update any result with their road map.
Before that we have find whether product he is expressing will have potential market, whether he tells capability to develop to the project. Whether they have good team for future developments.