There is no simple answer to that question, and every customizer will answer differently. Some basics include:
- X-acto knife & mat knife
- Superglue
- Acrylic paints
- Paint brushes
- Sculpting medium
- Sandpaper
- Pprimer
Ultimately, one could get by with the above list. However, in the interest of sanity, I highly recommend some or all of the following:
- Dremel
- Magic Sculpt
- Plumber’s epoxy
- Super Sculpey
- Silicone sculpting tools
- Various sharp pointy things
- Dullcote
- Access to a computer and printer
- Modeling paste
- Matte gel medium
- A full range of spray paint colors
- Masking tape
- Drill & drill bits
- Airbrush