Both approach has its advantages/disadvantages. It all depends what niche u're in. If it is a high demand, low bidding keywords, then go with PPC.
If it is a high demand, high keywords bidding, then you might want to use affiliate marketing techniques to drive traffic to the site.
Of course you can use a combo of both. Most IMs, will use a combo of both. The impt thing is to set a budget always & don't go overboard if you do not rank the 1st page of Google. I shoot for 5th to 10th position when starting out a new niche.