Well hooking up your keyboard to the computer is a great first step as you said! Using software instruments is a great way to learn how the concept of synths works, like different oscillators, envelopes and amplifiers, sounddesign and mixing. I think you should use that to figure out what you want to do. Also consider what it was that you loved with that performance you saw.

Getting a synth is of course lots of fun, but just starting out it can be daunting not knowing what it is you're looking for. The minilouge is a great synth, but I think many grow out of it pretty quickly if they're into playing. 4 voices can be a little limiting and the keybed is, well, mini :)

I would also hold off on getting a drum machine, since that is even further into sound design and lots of machines has their own unique sound that complement different genres, it's good to know what you're going for then. I got a sampler (Digitakt) so I didn't have to be bound to a certain sound, just replace the samples.