Bou is really good but pricey imho. But it was the first one I ever found. You can also get it through Amazon and Walmart.

RC Fine Foods is what my mother gave me as a present actually. They do kosher, vegan and low sodium flavors too, I just grabbed the first one I found on Amazon for a link. The veggie low sodium is my favorite.

Better Than Boullion is what I grew up on. But not all flavors are GF! Digging through online forums where people wrote to customer service, it appears that the beef and any low sodium versions do have wheat. The others they provided a vague statement about not including wheat, but how they do not test for it gluten so they can neither confirm nor deny.

As always if you're new, talk a doctor and write to customer service when in doubt. It does no immediate good for when you need something asap but the peace of mind is good to have.

Edit: the gravy I got was McKormick (sp?), it usually is $1.50-$3.99/ea depending on where you shop, but Walmart has it for either $0.78 or $0.88. So I grabbed a handful.