Advice for marketing online shop

A friend of mine is an entrepreneur that runs an online and in person business tuning German cars. While he has his own website and is very techy he doesnt have the patience or care to do IM so it's now in my hands to promote his business. Social media is my main expertise even though im still learning the ropes, but what else can i do to help his website grow? It isn't a blog simply an online shop that offers services and some products. This is a big opportunity for me to get some experience without having to break my own bank for the things i need.