Maybe not an immediate necessity, but once you start cooking low and slow (i.e. Smoking), I would highly recommend getting a BBQ Guru. I had done research across the internet for a tool like this and the wife caught wind that I wanted one, so she got one for me for xmas. I've done two long cooks with this since, and to be honest, it's changed my life :lol:
Once you graduate from a novice BigGreenEgger, you are gonna thank me once you get one of these.
https://www.bbqguru.com/storenav/gurucookerguide?DeviceModelId=25&ProductId=0
It saves so much time, frustartion and worry about checking temps on the grill and your meat. It pretty much guarantees a perfect cook. It will also teach you NOT TO TRUST THE BUILT-IN THERMOMETER THAT COMES WITH THE GRILL. (Hint: it's at least 20 degrees off).
Also, I highly, HIGHLY, recommend getting one of these instant read thermometers. It's the fastest, most accurate one out there.
http://www.thermoworks.com/Classic-...H7PGfiRdxfwWstyMX7s0vstut5jAUQna2NhoC7yfw_wcB