If I could do it over, I would have started CD'ing my twins earlier. We started at 5 months. I have a HUGE stash, much bigger than we need. Remember, with twins, you'll have enough for a wash every night or two at the most. We have 4 dozen PFs and 3 dozen fitteds. Part of that is to stock my parents' house, and it is a luxury, but more expensive than I would have liked.
Best yet, consider starting with a service while you get the hang of cloth and what your preferences are. Younger babies are more patient with diaper changes, and will peacefully lay on their back while you learn to be fast with a PF. Then when they're a little older and flipping on their stomachs, you'll want something you can put on upside down.
Get a diaper sprayer! It'll pay for itself in no time. I love my Potty Pail.
Twin CD'ing can be done!