Congrats on the Yoder, you will love it! ATBBQ sells BBQr's Delight by the pallet at a great discount and they are good pellets. You can also buy in bulk from Lumberjack, cookinpellets.com and others. So it's best to try a few brands and see which you like best, then order those in bulk. Believe me, you will use that baby a lot, so you will need the pellets.
If you want to buy bulk now, the safest bet is BBQr's Delight Hickory. That is the pellet that Yoder uses to test and program the pits, so you know they will work great for you. ATBBQ would be the place to order those.
Have fun and post pics once you get it.