hi am looking to travel to usa from london am a Indian Passport holder I am on a student visa .?

but i have a problem like in when i was in india i applied to f-1 visa twice my visa was provoked about an year back and the visa officer issued me 221(g) . do i have a chance to qualify for b-2 visiting visa in the future . and also will you please let me know how much funds i have to show to the visa officer in my account for 30 days trip

you need to be in india to apply for any kind of visa to visit the united states.

under 221(g) you still have a chance. please consider this: http://answers.yahoo.com/question/index?qid=1006050325183

moreover, for a 30 days trip you would need to show sufficient funds to support yourself, which would be around GBP 9000.

Here is addresses of USA embassy in UK, contact with them ,they should help you:
http://united-states.visahq.com/embassy/United-Kingdom/

also here is info about USA visa
good luck