I'm partial to O scale myself, as it's still pretty large, yet (sometimes) less expensive than G. But if you're looking for ease of putting a circle of track on a shelf around a room, the larger scale of G would probably be an advantage. I think it'd be simpler.
Before you plunk down any money, I do suggest going to the library and seeing if they have any books on model railroading. Most libraries do. A lot of the focus will be on smaller scales like HO and N, or on classic sets of the '50s like O scale Lionel and S scale American Flyer. G scale is a relatively recent phenomenon. But you might get lucky.
Check the different hobby shops in your area, definitely. Here in St. Louis there are four that I've visited more than once. One is super, super helpful, so I tend to visit him first even though he keeps the oddest hours. Two others try, but they deal in lots of other hobbies too so it's kind of the luck of the draw what kind of train help I can get. If you run into that situation find out when their train expert is working and try to talk to him. A fourth shop isn't interested in helping you if you have less than $1,000 to spend, so I don't go there much. Sadly, those shops exist.
Forums like this can be very helpful too. And since we're not paid on commission...
I guess I ought to ask you a couple of questions. First, of course, is what are the dimensions of the room and how high up do you want the track? Second, do you have a price range you've decided on?