Don't know why you chose this kind of promotion as it has been proven multiple times that it's counter-productive and usually ends in a bad way.
No-deposit bonus should be restricted for a small number of particular customers, usually reviewers, testers..
If you are to give it to everyone then many rules and restrictions should be set in place otherwise it's going to be massively abused.
If you are going to go with deposit bonuses then you should offer a higher match-up and a lower wagering requirement than your competitors to get a positive result.