I’m planning on buying Renoise soon and was wondering what kind of hardware is necessary or recommended to use in conjunction with Renoise (DAW software). For example, a MIDI keyboard etc. 
What is required? A computer.
What is recommended? The list is endless and depends on who you talk to 
A half-way decent audio interface and some kind of MIDI controller, probably something with keys and a few knobs or sliders, would be a decent enough place to start. Although not even that is needed.