Start out with about $200 to spend and don't bid more than $1.50 depending on what you are promoting. Make sure you set up a good landing page with no spelling mistakes, and make sure it is 100% relevant to the ad. You should get a good quality score and thus lower bid prices.
About 6 months ago, just for the hell of it one night at 2am..I looked thru my Shareasale account for hosting offers and started directly linking to the merchant's landing page. I think I bid like $2.50 a click to stay near the top and when I woke up in the morning at 11am I had 45 clicks and 11 sales @ $100 commission a pop. I haven't been able to reproduce those results again, so google must have fucked us over on something since then. Every time i try to put up hosting ads the keywords are $5-$8 a click which is outrageous.