I decide to make clear something that cased me some problems when I start blogging. In the matter of facts it almost drive me to despair.
Worst blog niches for making money through pay per click advertisement – they can make you suffer, believe me. Of course – if you get enough traffic on your web site you will make some money. In any case consider to try some other form of making money.
Gaming – especially gaming, maybe the worst niche for making money ever. My first blog was in this niche - very low revenue.
Entertainment – most global thing, music, video and of course all forms of gaming – low paid in pay-per-click programs. Advertisers don’t want to pay much and there are not many of them. Of course there are other ways for monetizing your blog that would work for them very well.