Honestly I would not buy into lighting, if your business does take up you will need professional lighting and the only way to get that (apart from spending thousands) is to rent it and include the rental fee in your fee.
As for controllers: The Mixtrack III is quite a good controller. If you want to expand you can easily add something like a reloop Neon and a few Serato FX packs to the mix. I would not upgrade from a midrange controller to another midrange controller. The more buttons you get from a SR you can easily get by adding the Neon.
Then when you have some more gigs under your belt, the gear will pay itself (for a decent wedding or mobile gig you should get at least 1k, minus 200 for rentals you still have 800 in your pocket).