Depends what exactly you want to do, but some of my go-tos are:
Snakebite Leather does a nice yellow-brown that's also a really good base for gold NMM, or works as gold on its own in a pinch. You can also paint it straight over acrylic silver metals for a quick old gold color.
Basilicanum Grey is likewise a nice grey that's also a good base for gunmetal NMM, or works as gunmetal on its own in a pinch.
Skeleton Horde is good for bones, teeth and also general pre-shading and toning-down.
Gore-Grunta Fur is a nice red-brown that's also good for general shading, dirtying up, and toning down brighter colors.
Volupus Pink is good for fleshy bits or, whachamacallit, distressed skin? Knuckles and elbows, shading under eyes, chafing, sores, that kind of thing. (That one's maybe more specific to my current Nurgle focus than the others, heh.)
It's also worth noting that for a lot of the not-just-painting stuff I mention a pot of Contrast Medium is a must. If you thin contrasts with water or regular medium they stop being contrast-y pretty quick.