SEO & Revenue (ad) systems: which are the best?

[Tragamin]

First of all, hello everyone, as this is my first post I've registered more than a year ago now, but only recently bought a vBulletin license so I'm still in the process of getting familiarized with some of the more advanced features in this amazing piece of software.

So, let's get to what brings me here today: I understand there are plenty of vB boards which incorporate banner and/or text ads here and there to generate revenue based on the number of views and clicks. Over the time I grew more interested in this but didn't really want to bother my members by cluttering the pages they view with publicity. On the other hand, I feel my site is not fully optimized for search engines, since I don't get the ranking I would like for certain keywords.

I was wondering if any person who's got some experience in both these subjects could give me some advice - for instance, is there any good mod I could use to manage an advertising system that hides the ads to certain usergroups? Because recently, I began to notice that most of my visitors are guests and remain so, although they're not allowed to post and view a couple of forums. I was looking forward to experiment with a banner and google ads in conjunction, is this a good idea? As for SEO, which steps should I take in order to achieve the best resusts?

Sorry for such a long first post, and thank you in advance for your time and patience reading this. Any kind of advice you can give me will be much appreciated.