For my tastes, it's however much will be needed to make playing the race a meaningfully different experience.
1. I'd like each race/lineage to have something that makes playing the race distinct that ties to some mechanics. The gnome's magic save; half-orc's relentless endurance, and lizardfolk natural armor all check this box; Dwarven stonecunning, or Elvish Keen senses, Trance, Fey Ancestry, and Weapon training do not. If it were more rare, Darkvision would fit here too.
2. I'd like physical size to be a more meaningful variable (so that playing a small character means you are physically weaker than a medium character, and did more than indicate how tightly you could squeeze and whether you can use a heavy weapon.) 5e chose not to pursue this because of (claims/perceptions of) balance between the races; I'd be much more interested if there was a flat -4 to strength, and there was no sense that needed to be balanced out.
3. If something points to a niche, then I want that niche to infect other character builds, rather than support the niche. (The best example of this is the Goblin in 5e, where with Nimble Escape every class gets to play a little like a rogue; the High elf's free cantrip can have this effect).
4. I'd like there not to be multiple languages that are only spoken by a single species (a Halfling or Gnome language adds little to the game; goblinoid and draconic are much richer). There are lots of changes to languages I'd like, though.