How involved do you want the process to be? If you want to pour the lead and spray fancy paint jobs, you'll need guidance from someone smarter than myself.
I'm not set up to pour lead, so buy the spinnerbait heads from Jann's Netcraft or Lure Parts Online (LPO). You can get them painted or unpainted. I buy painted.
You'll need wire forming pliers to shape the hoop for the swivel and blade, needle nose pliers just don't work for this. I think I paid $5 for a pair of wire forming pliers at a craft store.
When I order my spinnerbait heads, I also order silicone skirts at the same time. I have also tied up a bunch of spinners with flashabou skirts in various colors.
For blades, beads, and swivels, I harvest those off of old spinnerbaits that are too mangled to swim straight. I also search the clearance bins for these components. I also buy some new from time to time, when needed. Of course, new ones are available through Janns and LPO
I have found that, even with reused components, making spinnerbaits isn't that much cheaper than buying them. But you can assemble what you want and its an enjoyable process.