Mice are so easy to breed. If you go to a pet shop that keeps its male and female mice together, you can sometimes just pick out a preggo female and get a jump start. She'll be markedly fatter than the rest, looking like she swallowed a pingpong ball.
If not, then just buy a male and female mouse. A ten gallon tank with a secure lid is fine for two mice, but if you do it my way, you'll want to seperate the male as soon as you know the female is pregnant. The M can mate with the F. as soon as she gives birth, and that's very stressful on her body. I usually feed my males off after they serve their purpose.
I use Sunscription rat cubes, and toss in generous handfuls of cheap birdseed with the sunflower seeds in. Water needs to be available all the time; a water bottle works great for this. A half log hidespot for the female is good for when she is about to deliver, so she can have a secure nest for her young. Please make sure the lid is secure! Mice can squeeze through a half inch space. I use screen lids weighted down with jugs of water (the half gallon size, taller and thinner than a gallon jug, two per tank.)
I use hardwood shavings as a substrate. Pine is often downplayed because it supposedly has phenols that could harm the mice, but I never had trouble using it and it is dirt cheap. I would never use it for my snakes though.
Good luck!
To differentiate between male and female mice, is simple if they're adults. If your pet store is reluctant to sell you a pair because they figure you're breeding your own (and therefore potentially not buying mroe from them) then tell them this: one of my snakes only eats female mice, the other males.