I’m lucky I learned Spanish up to an intermediate level in reading because many books on magic have been written in Spanish and many of them aren’t available in English. It’s been useful when I search for information on Santa Muerte and, unexpectedly, Draconian magic. In fact my first Qlipothic book was the Spanish version of a multi-part series of rituals.
I’d be willing to learn Hebrew, Arabic, Japanese, Enochian and maybe French. I know a tiny bit of Japanese but I wish to learn more so I can read Shinto books in thier original language. Hebrew and Arabic are languages I like both in writing and sound and they both have magical qualities. Enochian is basically a language for magic and it’s widespread in use. A lot of Voodoo cultures speak French so if I have to learn it I wouldn’t mind since in writing it’s similar to Spanish.