I am comfy keeping smaller amounts of data inside my jails. I snapshot and replicate them to an off-site machine and I know how to maintain and upgrade them regularly. Keeping the data outside the jail specifically facilitates deleting the jail and starting over. What precisely needs to be "outside" depends on the application.
That being said I currently keep my Nextcloud data outside of the jail, but e.g. the repos in gitea all inside.
So your decision in the end. Thanks to local mounts you can even have /var/db/mysql on a dataset outside the jail if you are so inclined.
I would not mess with things too much in the beginning. Keep the stuff inside, but do set up an hourly snapshot task. So you can just roll back any mistake you might make. Re-arranging can still be done later, when you have gained some experience.
Specifically opening up your gitea to the internet will take some careful examination of the current setup, recommended reverse proxy, TLS, ... so for now just enjoy what you achieved. Congrats!
Did you go the avahi route for the hostname instead of IP address? If you do, you can even leave the jail set to DHCP, the IP address doesn't matter. IPv6 if available will be picked up automatically, too ...