Multi-niche site keywords and CPM

Hi people,

I've designed a site and I am uploading content to it each day. I'm proud of my efforts so far, but just had a couple of questions it would be useful to have answering to help me plan for the long term.

1) My site covers lots of topics (entertainment / unusual knowledge). As a result I'm not sure what the best keywords to target would be, as no one keyword, or even one area of keywords would really fit across the whole site. Would I be better off picking a keyword based on the content of each post and link building based on this or is there a better method?

2) My thoughts for monetisation were a combination of kindle (grouping together posts on a certain topic, rewriting and putting into an ebook) and CPM adverts. I'm fine with the kindle side, but have questions on the CPM side. If one person spends time on the site and looks at multiple pages would this count as multiple impressions? Also, the rate for just a single banner seems quite low. If I put several on the site (there is space for 3 or 4) could I earn more this way? Is there a general formula for working out how much money x visitors/page views would make?

If anyone could help me with these I'd be hugely appreciative!

Thanks

To 1) i would rank up the individual sites based on keywords as you mentioned