I agree with the poster below that Priceline might be a great place to start.
Mecca have more upmarket and expensive items which might be great if you want a really nice eye shadow palette for the 20yr old. Perhaps a Morphe palette. They have a selection for $36.

It’s worth checking out Priceline if you’re not wanting to spend a lot of money! In the past year or two, Priceline has really upped their game when it comes to the brands they now stock! Definitely stay away from products with acids as they really dont need it at that age.

A nice eyeshadow palette is a great idea. I love having a palette that has a range of nudes, browns and blush pinks. That range makes for versatile use. A nice brush set and skin primer. The Mecca Max range is excellent, high quality make up at an excellent price. It took some time for me to find skincare and hair care that works for me, maybe a gift card so they can do some exploration.