Sorry to not respond before Christmas was over.
In AV, I like to set it to f/11 or higher to get a little sparkle in the Christmas lights. f/22 produces too much sparkle, in my opinion.
Let the Shutter Speed do what it wants to do if you’re shooting from a tripod. It’s really impossible to shoot Christmas Lights without one.
I suggest shooting Christmas Lights at dusk, not dark. You get a rich blue sky which really adds to the composition.
Make sure to fill you’re frame with Christmas Lights.
Use as low an ISO as you can, too.