I do ok on fiverr $500 + a month on average for the past 6 months.
I agree with a lot of what is being said here.
A few rules I live by on fiverr.
If they ask more than one question prior to the sale, they are not worth it and should be ignored.
Offer a refund if they are not satisfied, just saying you are willing to refund goes a long way and refunding is easier than dealing with the a$$ whipping of a douche customer.
Offer something free, any kind of free bonus makes most people happy. Most of them will never read your free bonuses so feel free to offer all the bonus ebooks etc you like.
Make sure you find a way to get your best customers away from fiverr ASAP. The sooner you do the more you can up sell them and get more $$$$
Only sell things you don't hate to deliver. I can't stress this enough if you hate doing the work to deliver for $4 - gaypal fees it's never going to be worth the beating you are putting yourself through. Just because it will sell doesn't mean you should sell it.
Hope this helps.