Adbrite might be a good solution for you at this point. Adsense is more than strict but it is worth following the rules and getting on board at some point with that program. Considering the scenario that you have laid out it is best to wait for adsense. I think you should be able to go ahead and get an Adbrite acct. while you improve your guest traffic. Adsense is good but the market is tight and you will need a more than fair number of visitors to make it profitable. Adbrite will give you some good experience in the meantime.