How long does it take a dog to adjust to a new home? I am new to owning a dog. I have 3 cats and have always been a cat person. Recently, we got an 8 month old puppy and I was just wondering how long it will take for him to realize that we are his new owners and for him to relax a little in his new home? We made sure to bring some of his stuff from his old home and gave him a large area to be in, but he is gated off from the rest of the house and won't eat and just lays in front of the gate. So far, from everything I have read on line and heard from other people, this is the right thing to do, but I feel bad. And I am sure he can sense that!!

Welcome to dog owning. It really can be fun! When you say he is gated off from the rest of the house, do you mean he's off in his own room sort of thing? Dogs want most to be part of the pack, that's you, and he would be best somewhere that he could see you, in the kitchen or living room or wherever you spend most of your time. Encourage him(in a fun, happy voice) to follow you around the house, even if you have to tie his leash to your jeans, instead of keeping him in his own area most of the time, or alternate between both. If you are worried about him bothering the cats, I wouldn't as long as the cats are normal healthy agile cats with claws--they can pretty much take care of themselves when it comes to dogs in the house.
If you haven't already, get the dog into an obedience class, they can show you ways to make yourself his pack leader and thereby bond with him, and if you can't do that very soon, an hour with a dog trainer who comes to your house would be money well spent.
I hope you have taken him to a vet for a checkup. If he is otherwise healthy, the not eating will stop when he gets hungry enough. Try to feed the same stuff he's used to having, at least at first. If he hasn't eaten for a couple of days, make sure he doesn't then eat a whole lot at once--several small meals is best.