How much money would I need for three days in London?

Depends where in the city you are staying, zone 1 i pressume ? Just buying day passes for three days is all you need, so don't see the need for an oyster card if you're just gonna be here for three days- they make me pay for each oyster i've purchased you might save more money that way...i've lost 6 i should know.hehe.

good cheap food all over london, some of my favourites are the curry houses along bricklane...usually decently priced. make sure you give wagamama a visit - cheap and good chinese food.......

shopping- not just oxford street, but carnaby street, is pretty rad. i really like some of the cheaper stores like h&m ,primark, topshop, oooo and muji. be careful to not over spend....i do it all the time here... depends how much shopping you plan to do...i'd bring atleast £150...just me tho.......have fun!

Eating out during the day : Mortimer St. There are several £6 all you can eat for lunch Oriental buffet places.

Got to a pub : £2.75 a pint, average.

Shopping on Oxford St : Cheapest is Primark

Oyster Card : However much you are prepared to put on it. 99p- £1:50 a journey.

Well you do have to realize the currency system is different over there, and the dollar there isn't the same as it is here.So really just figure out your average spending where you are now then simply convert it to their currency and that gives you a general idea.

i would get £70 to be on the safe side