Which is better, PPC or Google Adsense? I just started my new website, and yes, I believe it is in the "Google sandbox".
Do you mean another PPC service such as Adsung, Bidvertiser etc to Google Adsense, as Google Adsense is Pay Per Click
You made a logical mistake in your question, if you ask if there are better PPC programs than adsense, I answer there are, but only for some people : some people prefer adbrite, adtoll, or the above mentioned ones.
Are there restrictions from using many different ones, or are you generally only allowed to use one? If the latter, which is the best deal?
From my knowledge, you can use as many PPC ads from different places as you want. But I do know some companies have a policy about this so if yours doesnt mention anything about collaborating ads with others, it should be OK. I know with adsense its not a problem.
Adsense is one of the better easy-acceptance programs. If you've got very high traffic and excellent conversion results, there are better but chances are that if you're asking on a forum then you don't make that qualification.