The shuttle train is mostly underground, just a few meters of track are far enough above ground to see any planes. But last time I flew (January), it was not operating because of terminal extensions, and shuttle buses were used.
At the gates themselves there's small WHSmith's, Costa Coffee, and some Sandwhich shops. Not much in terms of duty free - all that is behind the passport control before you enter the buses. There you will find Dixons and the usual perfume-sellers and duty-free shops.
Go's flights leave all over the place. But that doesn't matter: The two gates areas are identical as far as I can tell.
The airport is very light, easy to navigate and fast: check-in, passport control, luggage handling etc. are all at world-class speeds. The runway is fairly visible from the gates areas, but as there's mostly narrowbodies, it is too far away to take good pictures. The windows do reflect quite a lot like all airport windows do. But for a nice plane-watching it is sufficient.
To get from the piers to arrivals area, the same small train would be used, in the other direction. But they go every 3-5 minutes, so not all pax take the same train. Also, when the train does not work, 2-3 buses are used instead.
Enjoy your trip. Stansted is my favourite London airport to fly from.