[InFlight]

I would suggest the biggest lathe that your budget allows. Even a basic mini-lathe would allow you to machine custom drive shafts and spacers.

You should include a minimum set of tooling to get you started.

Cutting tools - Minimum of
AR & AL for 90° Edges and Faces
BR & BL for Turning edges
C for Flat side Turning
D for thread cutting
Cutoff tool

Tap & Drill Set for creating threaded center holes

If you don't have them already -
Digital Calibers
Dial Indicator

I'd also recommend a cutter set for C-Clip and E clip groves. but you could add that later.