You can show your foal a lot of things, make him discover new things in his early age will help you to have a calm horse not afraid of everything. You can get him used to brushes, trailer, saddle pad... the most important thing is to do things slow and to reward a lot for every little success!

For a foal you can buy everything you need to groom him, one or two halters, a saddle pad, and until you don't ride I don't see anything else 🙂