Personally, I would go with a really nice piece of jewelry. Diamonds, maybe.
But that's me. Other than having my ears pierced, I have never done anything permanent, like a tat.
But....I'm a granny, with really pale skin. I don't think a tat would look good on me.
Diamonds, however, do.
Congrats on your sobriety. Want to get a tat, get a tat. Not your sobriety date, though. How about a spirit animal? My son has two hammerhead sharks on his calf in a kind of a yin and yang position. It's cool.