I don’t have practical experience but here is what I think you would need:
If you plan to play a static, pre-recorded show, all you need is a playback device like your laptop and a PA system. If you want to do some mixing you’ll probably want DJ software and a controller or a DJ mixer. I don’t know enough to tell you about things like MIDI pads or Ableton but if that’s the route you’re going to need more hardware/software.
You’ll also need to cover your bases with the basics like a table or a booth, extension cables, power strips, gaffer’s tape, and a tablecloth or tableskirt.
You could focus purely on the music but I think it is a mistake because frankly most people don’t care about just the music. Lighting effects aren’t really all the expensive and they make a huge impact. ADJ just came out with Mini-Dekkers for about $100 which I think is a great deal. They have DMX so you can link them together, they strobe and they throw off RGBW light beams. Add in a small fogger and a light stand and you have a light show for about $300.
If you want to promote yourself you’ll also probably want signage, flyers to post up around the venue, and business cards. You should set up a webpage or at least a Facebook page so you can get feedback or keep in contact with show goers for future events. Personally I also think your appearance plays into this as well, your clothes, shoes and props are all part of theatrics that is part of putting on a show.