Basic equipment
1. Good dual action polisher (I have the Griot Garage 6). Get a smaller one as well for tight areas. Pads for both.
2. Vacuum
3. 3 buckets and perhaps a few bucket dollies. Grit guards
4. Steamer vs extractor. Do your research and decide how much you want to invest. You may choose both.
5. Ladder or platform ladder for tall vehicles
6. Carrying bags, detail bag
7. Towels. Lots of them and various types (waffle weave, General purpose microfiber, Griots PFM towels).
8. Tire and wheel brushes. Soft brushes for emblems. Lug nut brushes or Q tips for areas like this.
If you get a chance, attend a detail focused training like Detail Camp at Autogeek. It made me aware if items to consider.
There are several detailers who post videos on equipment, products and techniques (ie Darren, Scott, Junkman 2000, Ammo NYC, Joe at Next Level Detail, etc).
Just some thoughts on this Monday morning.