So far this year I've been steady at pumping out one hub a day.
I just recently dropped all eBay ads from my hubs because they have a horrible earnings per click ratio (probably because someone might bid but not win an auction).
If I were you I'd stick with Adsense and Amazon... and then wait until the HubPages ad program is widespread.
From what I'm seeing you'll make the most from the HubPages ad program because traffic = earnings. So far that's been the case for me.
Adsense will help you bring in a decent amount of money if you get enough traffic. I was close to making $100/month with them before they changed their algorithm. Some people on here make 5 times that.
And Amazon has been making close to the same amount of money for me as Adsense so far this year. But that's because two people bought ellipticals through me.
Just write a good amount each month, with good content and maybe drop a few links to your hubs at high PR places like Identi.ca and you'll build a following. Other hubbers won't be clicking your ads really BUT they will comment, which will look like new content to search engines and boost you up in rankings.