I think around $2,000 sounds like a reasonable investment to start with. I've made an account with
https://mtgox.com/, is there a better way to buy coins to start?
Also if there's any required reading on bitcoins that I don't know about, please share your wisdom anyone!
If you're going to invest any significant amount of money, familiarize yourself with Bitcoin security and learn how to keep your bitcoins safe, make sure you know exactly how to move your funds from place to place, familiarize yourself with the practices of any exchanges you intend to use and with the challenges you might encounter (e.g. identity verification, etc.), and familiarize yourself with how the Bitcoin protocol actually works.