Thanks all of you for the warm welcome and the great advice! I'm so lucky I found out this forum. You guys really give very valuable information. I guess I will have to see how much I can save...maybe if I really save up I can get USD1500 by the time I travel. Perhaps that's more doable. A friend who visits London frequently said it costs 30 to 80 pounds per day minus accommodation and minus shopping.
I'm sure there are college kids who backpack across Europe with less. I found some places on AirBnB for USD40 per night...the longer I stay, the cheaper it gets. So that leaves about USD60 per day for transport and food which I think is okay? I did Google but what I found online is more of a rough estimate so I still need to figure out details.
I do appreciate all your input though!