Hi Mauricio,
Welcome to 5 Star.
Yes true affiliate programs are ALWAYS free. If there's a charge it's something else and they are just calling it an affiliate program.
THere are many ways to do affiliate marketing. Ideally and traditionally affiliates have their own site, domain and generate their own content. But there are all kinds of other options.
"I´ve already started with one but I dont see it working very well despite I've done many things they have suggested me."
Does this program have anything to do with make money online, Internet marketing, business opportunity, work from home??? If so that's the problem. You are starting in the worst possible market for a newbie.
"Could you recommend me a good affiliate program for a newbie like me???"
There is no one way or best program that works for everyone. If there was everyone would be doing it and it would no longer work for anyone.
Stop and before you do anything else, read all the stickies in our newbie forum concentrating especially on any info you find related to picking your 1st niche. Only YOU can determine what the best niche for you is. After you read those, move to our niche forum and start researching some niches.
Right now it's like you are ask the generic question - how do you build a house. It's too big a question, too many variables and depending on the type of house you want to build our answers could be totally different. So 1st you need to decide what type of house you want, then we can give you specific answers based on that.
Once you find your niche, then you can ask the best way to start and if anyone knows any good affiliate program and our answers can be much more targeted to your needs.
Make sense?