Reddit mentions of Hot Wheels Variations: The Ultimate Guide

I use this book to find out which different variations are worth more. My collecting largely involves 1988-2010 items so this book covers most of it and you can see how the cars evolved across those years. I don't find any of the new models to be interesting, also I like finding ones that I played with as a kid as opposed to finding new stuff. But everyone has their own likes/dislikes and you should collect what you want to collect, not try to match what everyone else does. There are plenty of resources, also use the Wiki to search different things and try to find your niche on collecting. Best of luck!