I think if you are learning
ASL, it's not beneficial to learn how to fingerspell first.
If you are learning
PSE or SEE, then fingerspelling is a useful crutch.
I know some Deaf people who can't spell worth beans but they can sign ASL.
I know some ASL instructors prefer NOT to teach fingerspelling first. I've also read some of the literature supporting signs first, then fingerspelling.
Babies and small children learn to sign first, and fingerspell later. Or if they do use any letters they use them as grouped symbols, not as parts of a spelled word.
Just my opinion.