You can't just don't invest nothing... Clickbank is a powerful money making tool that can make you tons of money a month, but you can't make lots of money with it unless you invest some money.. Why don't you try CPA offers, especially e-mail/zip submit ones, try making money with those first and after you save some money and gain more knowledge just go and promote products on clickbank, or why not, create your own product and sell it.
You also have to take the risk of investing that amount of money, release your fears of actually losing the money and concentrate more on how you can gain more money. If you do lose all of your money, it's still something good, because you now have more knowledge about what went wrong and start tweaking. The thing is that YOU NEVER LOSE MONEY, you're always investing in you.