Wiring, binding post, and screws are required. Polyfill is optional, although 1lb per cubic ft can improve dampening. Do measurements, see which you prefer.

You need more clamps than you think. I recommend doing the whole build in one go.

Any wood glue is fine. Each type has a slightly different drying time and strength, but all are sufficient for a sub build.

I am not a professional craftsman, but I used these for my last sub build and things went well:

https://www.amazon.com/IRWIN-QUICK-GRIP-One-Handed-Spreader-1964720/dp/B001DK9JW6

To get a glossy black finish you will need to sand, use filler on the MDF edges, sand again, prime, and then paint. There is no shortcut to glossy.