Hey Chad.
Welcome to AC. I've been coming here for almost a year I guess and I'm not even close to having a handle on all the different types of filters yet and still have a lot to learn in many other areas. The flood of information you will receive can be intimidating but don't be discouraged. I know first hand that everyone here is VERY patient, LOL. buy a filter for a larger tank than you intend to buy and you know you'll be good now and when you decide to make changes later. read the sticky on cycling and lots of random threads.
One thing I recently learned here is that if you choose low light plants for now there will be a little less info to process. I myself am not ready to mess with co2 yet (more likely to be needed for high light plants). Good Luck.
P.S.
the most important thing I bought when I started was my API master test kit.