The Shoe.

     Necrotizing fasciitis is the flesh eating bacteria that can spread from a cut on your leg to your face and lead to death within 24 hours. It's not common, but it happens. As fast as that is, apparently, it's not nearly as fast as the rate of growth for a baby's foot. They'll go from a double-zero to a size two in the first six months! After that, it slows down a little, but not much. Why even buy shoes? It's not like the kid's running marathons anytime soon. Even if they were, it's not like the shoes would help. By the time they got done they'd need a new size anyway!
     Regardless, Trimfootco.com recommends that "as a general rule, foot growth should be measured every month for babies under one year, every 2 months for one to two-year olds and every 3 months for two to three-year olds". That's a lot of measuring. One way around this is getting shoes that mimic the bare foot. Robeez (pronounced Row-bees) claims to have shoes that act like the bare foot, and they're supposed to expand as your kid grows. While they're kind of expensive, they should last longer than normal shoes, so it might be worth it.
     Though this may not be interesting now, just think, this whole thing is solely about shoes. And no, that wasn't a pun. Imagine the infinite amount of onesies, bibs, diapers, socks, and heaven forbid you live in a non-temperate climate. Someplace with all four seasons, like the mid-West. What's infinity times 4? At the very least, you're up-to-date on the shoe thing.