SEM Rush is mainly for sniffing your competitors keywords and bids on PPC and can also give you an idea of where their traffic comes from if you’re unsure.
Firstly, you need to decide which part of online marketing you’re going to focus on, your budget won’t facilitate all facets of it.
Personally I’d go with PPC as it’s quickest and offers the fastest returns. Google ads, Bing ads, Facebook ads and so on. I’m just not sure if your budget is enough to cover spend and a decent freelancer to manage it for you.
You might also look at SEO, but that’s much more of a slow burner with no guaranteed returns. Your budget may be on the small side for a decent agency too.
Then you’re getting into things like email marketing and social which tend to be customer retention and reengagement as opposed to new leads.