Why these characters matter
The anchors worth learning first are the ones with the fewest lookalikes. Fullmetal Alchemist has 6 characters, all listed for 2003, where none hair appears on only 1 of them, while blonde covers 3 — so a distinctive hair colour is often enough to locate the right cluster.
Learn Alphonse Elric first, then the candidate it is most often confused with: Riza Hawkeye and Winry Rockbell agree on 4 of the five clue traits. That one comparison removes the most common failure in Fullmetal Alchemist mode.