Adwords Campaigns Set-up and Improvement

I already have some Adwords campaigns set-up but I'm no expert in this area. I need someone to improve my CTR, lower average CPC, and overall improve our results. This will likely include building campaigns, ad groups, ads and keywords in the most effective way, to set us up in the best way to achieve results. At first this job will be to set-up our campaigns properly. If I am happy with your set-up work then you will probably be engaged to maintain the campaigns on an ongoing basis for the future. We operate a marketplace website, where users can buy and sell a particular type of product. Therefore our operations are not as straightforward as other e-commerce operations. The products being sold on our site change regularly, therefore the set-up should be established so it can easily replicated when a new product is added by a user. We are an Australian business targeting an Australian audience, not a big international campaign.