I haven't had success with PPC from the major search engines, but I have had luck in the past with a site called 7 Search.
It's much easier to use than Google Adwords. A little cheaper. Very responsive for Work at Home, Internet Marketing, Health, Dating, Golf-related niches.
No quality score to deal with, thankfully.
It's pre-paid, meaning you have to have at least $25 to start an account with it. Once the $25 has run out, it's up to you to re-up it.
Compared to other smaller PPC sites, 7 Search is strongly against click fraud. So if you spend more than $100 a week in advertising, they're going to want you to fill out a form and paperwork, credit card details, ID, etc.
I just kept it to $100 or less. Don't be surprised if you see reminders. Just ignore it and keep within $100 a week or less.
7 Search works best for getting people into your list. I've had trouble just trying to do straight sales, but list-building...not bad. Not great. But not bad. You'll get sign-ups.
Plus, the banner ad you use is long. So you can put whole sentences in the banner.
They also have a feature called Smart Bid. You don't need it. All you've got to do is bid high enough to stay in the top 3 positions. That's easy to do; out bid by 1 cent. I've had all my keywords in position 3, and I still got hordes of clicks.
You don't need that many keyword either. When you start choosing keywords, 7 Search will tell you how many clicks you're expected to get. Choose anything 3-digits and up, you should be fine.