Hi Michelle,
You can buy those I love NYC t-shirts in the official New York shops - they sell mugs, fridge magnets, t-shirts, calendars etc and you'll see a fewe about on your travels.
As mentioned prices do depend on what you are shopping for. I think your budget will be fine. I found Clinique and Estee Lauder a lot cheaper than the UK BUT don't forget to add sales tax to the price (can't remember how much it is). I only bought clothes in one shop ( J Crew) - hubby got 2 pairs of trousers, 2 pairs of shorts, 4 t-shirts, 2 shirts and a jacket whilst I got a pair of trousers, a dress and a skirt and the bill came to around £300 which I thought was pretty good considering all the stuff we got.
Food I found reasonable. Eating at a deli can be good value, we got a huge lunch - sandwiches which are massive over there (only made that mistake once!), fries and drinks - for £20, brunches (I'd recommend Landmarc at the Time Warner building in Columbus Circle) are great. We had a 3 course meal with wine at Garage restaurant for around £50. My main advice would be to avoid eating around the really touristy places - look for something where you see locals. Ask your receptionist - we were SC and as we'd had a big lunch, just wanted a snack before our broadway show and he recommended a local deli that did takeaway and it was really tasty and incredibly cheap.
Alcohol is expensive though. We had 4 rounds of beer (4 pints, 4 halves) in Heartland Brewery and it cost us £30. My berry champagne ale was very nice though!
Hope that helps.