Can a teen take this vitamin?

I’m 15 years old and I have a hard time recalling stuff.

I’ve been eating healthy things like fruits and vegetables but it’s not enough.

So I came to a conclusion about taking a vitamin (ginkgo biloba) like a book suggests. I went to a Walgreens to buy it, but on the bottle it says “not for people under 18.”

Should I still buy it?

Or is there a vitamin that helps improve memory?

I didn’t ask the pharmacist there because she was busy.

Thank you so much!