Alright, let me break it down in a way that helped me when I tried to figure out where to jump into the manga after watching the show.
The 51-episode 2008 anime of 'Soul Eater' follows the manga pretty faithfully for its early run — roughly the opening arcs — but it starts to drift away and becomes mostly anime-original somewhere around episode 30. In broad strokes, the anime adapts material from the manga’s beginning up through the early-to-middle volumes (think roughly volumes 1–7 or so), covering the introductions of Maka, Soul, Black☆Star, Tsubaki, Death the Kid and the basic Meister/Weapon training arcs. After that point the TV series branches off into its own plotlines and a completely different ending than the manga.
If you want a practical jumping-on point: many readers suggest starting the manga around volume 8 or 9 (which corresponds to the late 20s–30s in chapter numbering) if your goal is to continue the story beyond what the anime shows. The manga itself continues much further, wrapping up the original canon in later volumes, so expect to find quite a bit more depth and a different trajectory for a few characters. Honestly, once I started reading from around volume 8 I was hooked — the tone and stakes feel more consistent with the manga’s vision, and certain character motivations really pay off, which made me glad I picked up the books.