Applying visit visa (B2: Visitor for Pleasure) to US. documents clarification

[Devayani]

I am going to apply for a visit visa (B2: Visitor for Pleasure) to US. Among the documents required for processing visa i want to clarify the following requirements. i am a Permanent Resident from Sri Lanka living alone here

    * PROOF OF SUFFICIENT FUNDS TO COVER ALL EXPENSES WHILE IN THE U.S.

How much money should i show in my bank statement of account?

    * PROOF OF TIES/RESIDENCE IN A COUNTRY OUTSIDE THE U.S. WHICH HAVE NO INTENTIONS OF ABANDONING.

Wht documents should i show?

    * EVIDENCE WHICH SHOW THE PURPOSE OF TRIP.
Wht evidence should i show? i dont have any specific reason to visit US. just curious wht is on the other side of the border
tks in adavnce