Bare minimum:
Couple of tyre levers.
Valve core extractor.
Spanner or pair of pliers to undo the valve stem nut.
Pump.
Washing up liquid/car shampoo.
Local Machine Mart or (probably) Halfrauds. Or eBay.
More or less any will do if you're just doing it in your garage - big, long steel ones are cheap, but don't use the leverage to compensate for bad technique and damage your tyres or rims
I have spangly Motion Pro spannerlevers, which are not cheap, but worth it if you want something light and multifunction to carry with you.