I got a pellet grill last year, here's some things I learned:
Most YouTube BBQ channels are stick burners, in other words huge offset smokers burning natural wood. However, you can apply their recipes or ideas to your new device. Some of my favorite channels are: Chuds BBQ, Mad Scientist BBQ, Meat Church, Smokin' Joe's Pit BBQ, The Dawgfatha's BBQ, and the Bearded Butchers. There are a whole bunch out there
For your first cooks go with simple stuff, like chicken thighs or breasts. Don't try to start off with a brisket.
I use simple rubs that I make myself. Good ol' SPG (kosher salt, coarse ground pepper, and granulated garlic) is easy to make and gives you good flavor. Two parts pepper, one part salt, one part garlic is what I use. You can build on that with other spices.
When you use BBQ sauce put it on at the end of your cook, otherwise it will burn.
Cook to temperature not time. Every piece of meat will be different. Poultry you want to get it to 165F. Pork is safe at 145F, but if you want fall off the bone ribs you want to get it to 200F.
Invest in a decent digital thermometer.
Let your meat rest after taking it out of the smoke.
Use nitrile gloves when working with your food so you don't need to constantly wash your hands when ever you touch meat.
Sharp knifes are a must! A 6 to 8 inch boning knife will be your most used.
Get heavy duty aluminum foil so holes won't get poked into it easily.
For beef use a minimum grade of USDA Choice, USDA Prime is better if you can afford it. The reason is fat is flavor and intramuscular fat will be more tender as well.