With multitools, the cheap ones often have very soft metal. Are there any extra bits you will never need. In my experience you almost never find good bike specific tools in yard sales but do find good grade allen keys, wrenches, pliers, screwdrivers and other basic tools. Good cheap tools are better than bad cheap tools.
A rear luggage rack turns the bike from a toy into a tool. You can pack a fairly good load of shopping in 2 large pannier bags so turn every shop into saddle time.
Again there are lots if very poor racks that are complicated. Keep it non adjustable height , open frame top, no propriatory rail system, good triangulation. A rear lamp bracket is the best place for a lamp.
I like to keep a stash of essential spares a couple of tubes spare cables brake pads so I can shop for them in sales and replace parts when needed. If you find a spare helmet that fits your head shape well always good to have in reserve. Helmets degrade over several years esp if dropped.
Gloves or mitts: never ride without them. Ever.