I'll be brutally honest. I think thats a terrible idea.
Members should be able to judge for themselves there abilities. If I went to a graphics site as a new member and found all the top tips were hidden from me and I had to work my way up through some kind of reward system I wouldn't stick around, I'd go straight to another site where I could find the answer I needed.
By all means seperate tips and competitions into something like a Beginners forum, and Intermediate forum and an Expert forum but dont hide them. You should remember that there will be people at the site (as well as new users) who actually are better than your "experts" or at least as good, its just they dont spend hours making things for the site.
If you implement a system like that you're just putting a big bottleneck on getting members.
