I try to avoid buying unnecessary stuff, but failed last year.
In summer 2020, despite the pandemic induced shortage of bike stuff, our local REI was blowing out some Shimano and SRAM stuff cheap. Nothing I really needed. Some BB-UN55 bottom brackets for less than $10 each -- I bought three in sizes my bikes could use if I decide to replace the caged bearing/cup BBs with the sealed cartridge bearing stuff. They had more but I didn't want to hog stuff I wouldn't actually use. And some HG53 9-speed chains -- I bought two for around $9 each. And one or two SRAM 8-speed chains for maybe $5 each -- I typically get KMC Z72, but the SRAM version appears very similar.
Turned out I did use the HG53 chain, on a 2014 Diamondback Podium 5 carbon frame I got from a friend and slapped together with a mish-mash of 7, 8 and 10 speed components. The nominally 9-speed chain worked fine, better than the KMC Z72 8-speed chain I started with.
Kinda wish now I'd bought up all the Shimano 9-speed chains and other stuff they had. But I got enough spare doodads to keep me busy for awhile.
And I bought some ugly but functional bar wrap cheap. It'll do to test wrap handlebars that I'm not quite settled on, before using good wrap for the keeper.