Definitely get an octopus card if you'll be back in a couple months.
For shopping, there's a Shanghai Tang close to the star ferry terminal on the Kowloon side.
The lines for the tram to the peak were nuts when we were there earlier this month. Uber was the way to go - they're cheap and plentiful.
Also be prepared for your ATM card to not work. Citibank ATMs saved the day for us.