How to find the right foundation shade?

Hey ladies! I was wondering how to find the best foundation shade? I’ve always struggled with finding my shade, it’s always a little too light or a little too dark. I’m pretty pale but porcelain is too light for me and fair seems a bit too dark.

I ordered some foundation and concealer the other day, the concealer is closer to my tone than the foundation, but like always I’m having the same issue, the foundation is a bit too light and the concealer is a bit too dark.

Could I mix them to make a color or should I avoid mixing them incase they’re different formulas?

How can I find the right shade??