Most of the git aliases people share online are the ones they wrote, felt clever about, and used twice. The useful ones are boring, and you can tell which is which by whether you'd notice them missing on a new machine. Here are the four I'd notice within the hour.
[alias]
st = status -sb
lg = log --oneline --graph --decorate -20
last = show --stat HEAD
unstage = reset HEAD --
st is status with the short format and the branch line, so I get the whole picture in five lines instead of the full paragraph-per-file lecture. lg is a one-screen graph of recent history, capped at twenty so it never floods the terminal, which is the difference between glancing at it constantly and never running it. last shows what I just committed with the file stats, which catches the classic "did I actually stage that file" mistake before I push. And unstage exists purely because I can never remember that the command to undo git add is spelled reset.
That's deliberately it. I used to have a wall of them, including some genuinely fiddly ones that strung together three commands, and I deleted all of those because I never trusted them under pressure. An alias I have to stop and verify is slower than typing the real thing. The ones worth keeping are the short, obvious shortenings of commands I run dozens of times a day, where the saving is small but the friction removed is constant. Clever can stay in a script with a name and a comment.