As I am newbie here can I join any bounty? And if yes then what I get from it?.
Yes, you can join any bounty campaigns, especially social media ones since most of these do not require one to be in higher ranks as long as you have many friends or followers in your account, even if you're a newbie, then you will be allowed to join.
What do you get from it? Well, you get compensated with tokens, either ERC-20 or Waves tokens. Depending on what campaign you are joining.