Never under estimate the power of marketing to your existing customers.
Huge amounts of companies, spend all this money and time to bring in new customers but then once they've purchased - neglect them. (some research has shown it costs 5x the amount to acquire a new customer than it does to retain a current customer)
Your current customers are guaranteed hot leads, they are 100% interest in your company as they've already purchased, they know the quality of your service/product and are more than likely happy to reuse you, again and again.
A key way of keeping in touch with your current customer base and retaining these is by email marketing. There are loads of different ways that can be utilised, be that by emailing customers that haven't purchased a product recently a free delivery code, or updating customers about events that are local to them and simply emailing them when a new product goes live. This builds the relationship between you and the customer and can result in a repeat customer and greater spend from that one person.