Greetings KHTM,
Let me share with you some of my experience in online marketing. I work for an online company which markets almost primarly based on PPC (Pay Per Click) search engines (Goto.com, Ah-Ha.com, etc.). The company is *cough*bathwise.com*cough* and what i can tell you is that we spend several thousand per month on PPC's (while it is effective if utilized properly, it's not always cheap). #1 Rule in directing traffic to your site is (especially) with PPC engines you want to target your specific market (for instance Bathwise targets DIY'ers, contractors, etc..). I'll tell you right now numbers don't lie, but they don't always tell the whole truth. I began marketing for Bathwise recently and when i first went into Goto i saw we were utilizing approximately 400 keywords. Now, 400 keywords is a lot of shiat and believe me a lot of those words weren't directed at our primary market. Not only did the additional keywords cost us a lot of money, but it caused a lot of problems. We constantly get phone calls for products that we don't stock, because our keywords are misleading (not good business practice). So, i believe your main concern would be to figure out exactly who is your target market (demographics, trends, etc) and do your research as to where you can most effectively utilize marketing dollars.