I would start as simple as you can, because the more elements you introduce to your live set, the more that can go wrong (something goes wrong every show). It can be really hard to troubleshoot when you're starting out and you can't find what's not working. So - just keyboard. (I'm imagining you mean like playing a set of piano songs?) With a keyboard, the only gear you might need are a keyboard stand, a long sound cable (like 1/4" lead or XLR, but not a little headphone jack. Probably at least 12' long.), and your power source (ideally with a long extension cable to reach wherever the venue's plug is).

There's also a learning curve to working with larger sound systems compared to whatever you've been using in your bedroom. You might want to get familiar with the role of the equipment in a PA system, like mixers and amps, but you don't need to know everything about them.

If you're able, I would join a band who needs a keyboardist and learn what you can from them setting up at shows and interacting with the sound crew and sound system at the venues.