choose a sign language
There are more than 300 sign languages in the world, and they are not dialects of each other. An American signer and a British signer cannot fingerspell to one another — the alphabets are unrelated. Ten of them are here.
why the alphabets differ so much
ASL, French, Spanish and Brazilian Sign Language all descend from the system taught in 18th-century Paris, so their letters rhyme. Learn one and the next comes cheap.
British, Australian and New Zealand Sign Language form a separate family with a two-handed alphabet. Japanese Sign Language is a third family again, related to neither.