I bought a few things on Ebay.
I use these are a lot:
https://www.ebay.co.uk/itm/Premium-Test-Leads-4mm-Banana-Plug-to-Moulded-Crocodile-Alligator-Clip-1m-UK/122041130073?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649My banana to banana leads came from China, but seem not to be listed anymore. Aim for thicker cables with silicone insulation.
Anyway, depending on what type of work you will be doing, consider buying:
A pack of dupoint style wires for breadboarding and pin headers, Male-Male, Female-Female, Male-Female short and long. Might as well get some pin headers strips too.
A set of breadboard jumpers, these can be made from single core below, but you can buy packs from "Wisher" (and others) already cut and formed for breadboard spacings.
A bundle of "hook up wire" in multiple colours. Solid core stuff is handy for breadboards and protoboards, multi-strand is better for inter connecting parts of projects.
Reusable banana connectors and croc clips. Sometimes none of the leads you have will do, so you have to make your own. Sometimes you can't trust the leads you buy won't turn out to be 3 strands of aluminium, but buying some 16AWG silicone wire and your own connectors means you know what you are getting/using.
Some decent high-ish gauge silicone wire 12-18 AWG for making higher current leads and PSU tails.
A multipack of those DC barrel jack connectors with connector blocks on them! Very handy.
A pack of 3 way tool-free connector blocks, they have spring loaded connections, very handy.
Wago(tm) connectors can be handy, though not essential, could be subsituted for/with the above. They aren't exactly "cheap".