I'm a newbie myself JSpence3. My dad always says "buy first what you'd buy last and you'll save money in the process by not continually upgrading your equipment." Well, that probably goes for smokers too.
In my case though I am using what I had on hand, an old 22" Weber One Touch Kettle. For $70 delivered my wife bought me a device off Amazon called "The Smokenator." Turns any 22" Weber Kettle into a smoker and does a dang fine job of it. Although it is basically a bent piece of stainless steel with a few holes, a water pan, and a stainless kebob stick for stirring coals, it does a great job of keeping the heat and smoke circulating properly and is a breeze to control the temperature.
With your $300 you could buy the following:
a. 22" Weber One Touch Kettle: $149
b. Smokenator: $70 delivered.
c. Maverick ET-732 Wireless Digital Dual Probe Thermometer: $60
d. 2-20 lb bags Kingsford Charcoal: $13
e. 5 lb bag of your favorite wood chunks: $5
All you'd need is a chimney starter for $10 at Home Depot and you'd only be $7 over budget!
The one drawback to the Weber Kettle is there is no insulation for winter smoking. Well, I plan on recruiting my wife, someone who knows how to sew, and turning a cheap welder's blanket into a dome insulator. Problem solved.
I'm sure the more experienced smokers will give you much better advice than me. That's what make a place like this great! It's all good!
Have fun shopping for your smoker, whatever you choose!