For one snake, I wouldn't breed mice. You'll be overpopulated in a few months, even if you freeze them.
Not to mention, just the cost alone will not be justified. Plus, the headache of breeding mice in general.
If you are going to do it, then yes, a 1.3 or 1.4 group would work. You have to be prepared for what you are going to do with all the babies, they cannot stay in with the colony, or they will start to eat pinks, etc etc... It's really not worth the trouble unless you have several reptiles...
My mom wants to start our cats on f/t diet too, so she's been asking me to breed the mice for a while. So, what will I need to keep the mice in? I want them to be happy while they are alive....