midi controller

I want to try to compose a song and I would like to do it on the keyboard / piano keyboard (and not through a tracker - this is the only way I know from the Amiga / Protracker times) and I only have 100 USD. What equipment should I use? It should cooperate with the computer, which means MIDI...

I'm using M32C with a Waves Soundgrid Card to run SuperRack and plugins. Up till now I've been using a mini PC with a touch screen for controls but I want to add a Waves Fit Controller. This needs to be connected by USB but since I switched Card I don't have a USB anymore. Or can I use the USB...