Agreed, large spools are too much if you want to play around with all the colors. I have a box of old filament, each spool in plastic with a dry packet and the whole box with a couple of bags of drying stuff and a good seal on the top. But after getting a spool out to use recently (spool about 2 year old) and it printed like shit. I tried putting it in a dryer, but it didn't help. So I tried more of these spools and they almost all seem to have gone bad.

Such a shame, I should have bought smaller spools, but they are harder to get and often more expensive.

I buy samples from Atomic Filament when I don’t know which filament would work best for a project. They are 50g spools for under $4 each. It is usually enough filament to print out a filament sample card and a small test piece.

You could try a filament sampler pack, but this might be too little of each color. Maybe buy a few packs 25 Colors Silk Shiny PLA Filament Sample Pack

PLA as a raw material is really cheap - you can get it for as little as a few dollars a kilo - and a lot of the cost of a filament roll is just making the spool, packaging, and shipping it. In the end, the price difference between 250g and 1kg of PLA on a roll is rather tiny. Goes the other way too, you can buy 5kg rolls that come down to just $10-15/kg.

The same reason why a can of cola is so expensive compared to a big bottle.