My Serissas live outdoors for the mid-spring through Autumn.. and it’s pretty cold here, too.
Just got BACK above 0DegF a couple days ago.
But if you’d like it to survive indoors, solely, it’s one of those species that IS “do-able”
Now, for the “which tree” “which state of development” “For a beginner” situation..
There a many options available for you. I believe (If not “tree hunting” savage-style) that maybe “meeting in the middle” and purchasing a nice piece of landscape nursery material.. and attempting an initial shaping/pruning/styling based on the attributes that “drew” you to the tree, might be a good “way to go”. Tis’ a good choice. not too pricey.. lots of options... established root(sometimes rootbound, though). Plenty of “...from Nursery Stock“ Videos available, as well.