There are really good reasons that the affiliate networks for accessing retails can company steep commission levels. There are also really good reasons that hiring a experience sales person in this market space is going to be a significant monthly expense.
Retail Expensive to Penetrate
Retail is a crowded market with a significant number of vendors consuming the oxygen of attention of your target customers. Relationships are paramount. And there is a revolving door between the target customer s and the sales people selling to the target. Success rate is so poor on an individual basis that each hit is paying for lots of cold calls, failed proposals and "we will talk to you next quarter"
A Marketing Plan
You are going to need a "go-to-market" strategy which has been developed as part of the marketing component of your overall business plan. In this plan you are going to need to narrow the initial focus from general retail to a very specific target. Hopefully this will be a target which has a natural affinity to your product and team. You will also need to develop some targeted geographic areas. Once again hopefully this will overlap some resources available to your team.
A Pallette of Tools
As you customize the core value proposition to each of the particular market segments you are going after you will begin to find mediums and examples which will tell your story easier than others. this will guide which tools you use. As you pointed out there is SEO, PPC, Display, social advertising and general web. In addition to these your overall mix will need to also include: Business associations, networking groups, conferences, cold-calling, door knocking, networking, and guerrilla marketing.
These individual tools will be organized into specific campaigns. There campaigns will be structure to provide you an opportunity to track the results and develop the metrics associated with your "pipeline" This information will be critical polish and improve your marketing/sales engine. (A good way to learn this structure is to build it out within an existing CRM)
Build On Success
In your space -- I believe that you will need a track record and case studies of happy customers. Your first ones will be the most difficult to get. You are going to need to use every trick in the book to get the fist 5-10. You will need to bend over backwards to make sure that they are the happiest people in the world. You will make no money on them. You will however build the portfolio, case studies and references you need to close other retailers.