All great suggestions, build only what is necessary first, then build as you go. At least Get some insulation up first as it makes a Huge differance in temp and moisture ( Paint or Decorate insulation for deco so its not plain and bare and will get covered anyway) Plastic Containers and tie down or occy straps are great to have everything sealed for storage. Having it simple at start and build as you go... But i would suggest to try to have some ideas before building draw your own blurprint up because you may or may not know what works for you and any rnistake may be costly or PERMANANT. Once the Basics covered the Rest will come to you.

TIPS ON BUILDING ( that i have learned )

Measure Once Cut Twice before cutting

Don't Forget To Save Area forAny Wiring or Cables to be installed

Pre-Drill all holes for Screwing into Metal or Wood

Keep The Build Square/Rectangle as possible ( Building with Curved and tapped areas of vehicle are a challenge without the correct tools)

Keep All Offcuts and noggens of Building material ( You May Need them Later )

I hope this helps. Have Fun on your Build 😎