Finding a good ad provider seems to be exceedingly difficult :/
It's completely true that most of these networks run offers that are the 2nd tier "enlargement" and "weight loss" fare -- that sort of thing is probably 75% of their available offers and 99% of their revenue. But a good pub on a top CPA network can make a lot more money than a good pub using Adsense.
Your best bet for finding someone who is big enough to have offers, but not so that they turn people down. Try Commission Junction for a proper 'place CPA banner Ad' type setup.
They'll (probably) have you.
Once you're reliably making a few hundred to a few thousand a month, then you'll be able to waltz in to Adzoogle and any other affiliate network you want. As it turns out though, a lot of the smaller 'niche markets' are as good or better than the big guys.
Maybe sign up for offervault to get the names networks you want to apply to based on the offers that they carry.
Firstly, I strongly believe that all of the niches you can find make money. Seriously, you see the same ones on every affiliate site and if they didn't work, they wouldn't keep putting them up there.
If you believe in e-cigarettes, if you believe that through whatever channels you try for you can reach smokers who would like to try e-cigarettes, and you believe you can get enough 'buyers' to make your spend profitable (eg: $20 on ads and $30 in sales) ... then e-cigarettes are the niche for you.
Well, within reason - you've then got to turn your faith into facts via testing.
Second, because I'm only in the very early stages of my affiliate marketing 'career' - I have a lot of background experience from working around brilliant world-class affiliate marketers, but the devil is in the details. I'm not yet confident that I know the niches to move into if I gave you advice I could be steering you down the wrong path (every niche makes money, just got to figure out how).
Your best bet to have real experts teaching you the answers on where & how to get started is probably something like warrior forums.
Also, check out Mike Colella on mixergy http://mixergy.com/mike-colella-adbeat-interview