PPC Advice/Campaign Start Up

Looking to set up a PPC campaign using Google, Bing, maybe a 3rd tier like 7Search. We are competing in the property investment niche, so lots of competition. We are looking to be able to gain traffic without paying what the big boys are paying for searches, ( aren't we all?). Looking to start slow to gain an idea as to overall value, will spend more when we see directions that will be beneficial. We sell globally so not just looking at the UK.