In the inner corner, outer corner or as eyeliner. You can also pick a color that suits you really well (for me it’s green) and dust it over. What I also do sometimes is take a satin shade (let’s say green or or pink for me), spread it all over my mobile lid, and then take some gold and go above, in between the eyebrow and the mobile lid.
Largely, it depends on your eye shape what you can or cannot play with.
Buy makeup products you are certain the other person wants or will certainly like (if they express preference or a wish for something specific). Otherwise you risk buying them something that they will never use, because ppl are very particular about what they put on their face.
Perfumes are tricky, even if you like a scent now, tastes could change. It may settle on the their skin differently and they may not like it. Only buy a perfume you are certain the other person wants, has tried, and is in love with.
Clothes are, again, tricky. For obvious reasons. Even if I see you gorgeous in pink, you may not like yourself in pink sort of issue
Therefore gift cards are usually the best bet. Or something of sentimental value. Or something you know the other person needs (my friend needed an umbrella, so I bought her a beautiful one)
I myself have huge issues with stupid gifts that collect dust in my house. If you cannot buy something useful, give them a gift card to a shop you know they like