To be fair, if you want to succeed in Internet Marketing, you do need to buy a number of products to understand how the market works, what's out there and what these products look like.
You also need to get a sense of what is a good product and what's less than stellar. Let's say you buy something from Clickbank and you think it's totally useless. All you have to do is send an email within 60 days of purchase to refunds@clickbank.com and they will refund your money no questions asked. If you have your original email receipt simply forward that and say refund please as the subject.
I'm always amazed at how people won't blink at spending $5,000 for a college semester but freak out at spending $97.00 for a CB Money Making Product. If the product is no good, ask for a refund. If it does provide value, buy a couple of similar ones to get a more 360 degree view of the market (usually these products are similar but from a different angle).
If you are tight for money, speak to a friend or a relative and see if they would be willing to share it with you, or at least lend you the money that you can pay back out of profits.
If you're just tapped I'd follow some of the gurus and sign up for their list. They give away a ton of free information and while it might take six months of looking at their free stuff, watching their videos and listening to their audio calls, you will start to understand the process without having spent a dime.
What you really need to focus on is building a business. Don't hop around and sell different stuff... focus on business! You'll make more progress in 3 months of doing this then you will in 3 years of hopping around trying different stuff.