One of the best things I did a couple years ago was buy about 150 bucks worth of nuts bolts and washers.
I have more 'random' nuts and bolts than most guys who don't run a retail shop, but I never seemed to have what I needed.
I went with E-bay vendor, made a deal off E-bay with him for custom amounts and custom selection. Have NEVER regretted it, not for a second.
I don't always have what I want, sometimes not even close enough to use, but has saved me more than 50 trips to the hardware store in less than two years.
Each of those trips would have cost gas. My closest store is/was 5 miles, next one at 6 miles, next one at 8 miles. Prices are in that order too, the most expensive at the closest, up to the cheapest at 8 miles.
A washer is 20 cents, 16 cents 11 cents. So 90% of the time I drive the 8 miles each way for stuff. Get 60 x 20 vs. 60 x 11 and you can see why.
So 16 miles of driving adds 3.00 bucks gas to even a single washer.
Washers from the bulk buy average 3 cents.
More important, time saved walking over and getting the right thing, rather than searching my trays of bolts/nuts to find one or worse two to ten, that are 'not too different'.
I find myself putting temporary stuff together with the handy bolts, then salvaging them back out. Without a large ready supply of fasteners I would never even try to do that.