Should I gamble and utilize the initial free bonuses for new players offered by online bookmakers and casinos?

I recently turned 18 and this looks a good way to make a small sum of money since there is many sites offering great bonuses. I understand there is wagering requirements but still I have a high bankroll and will be smart about it and gamble with my actual money as little as possible. As soon as I win and get the bonus I will withdraw and never play again on that site. Have any of you done this? thanks in advance.