I take a fat drill bit (fattest in a decent set of regular drill bits, not holesaws) and put about five or six holes in the bottom. They won't lose soil like bigger holes without pot shards or rocks over them and the quantity will keep it draining freely.

I would find a good outdoor potting mix. Kellog's is available at most HD's or Lowe's, already mixed with earthworm castings and the like, might want to put in some extra perlite. Good nurseries also have a similar blend, particularly Black Gold, which I've heard is the cat's meow but haven't used it yet. You'll need a 1.5 cu ft bag or 2 cu ft bag. I don't think they generally do them by weight. Doesn't hurt to have a bit left over. You'll have another miniature within a month once you get the bug. LOL.

Suz