I've found that it's very difficult to get shoppers to go up to a second level. I've tried stairs, ramps with big arrows, teleporters, gimmicky things like ladders & ropes to climb, etc. But people just do not like to go up! So I'd recommend staying on one level, if at all possible. I sell horses and animals so like a wide open space. When I'm out shopping myself, I prefer a big one room shop rather than one with small rooms branching off everywhere and I especially dislike low ceilings. Good luck with your shop!