A dated copy of the official program description as read on the day, the full file for the pending petition including receipt notices and the petition basis, and any written material a consultant has provided. Keep the consultant's material specifically, so it can be compared with the official source.
Preserve the record of what you were told
People rarely keep promotional material once they have made a decision, and it is exactly what an attorney needs in order to see where an applicant's understanding came from. Save the emails, the brochure, the slide deck, the recording if there is one. Alongside it, keep your own file for the existing petition: the receipt notice, the category, the priority date if one exists, and the employer's supporting documents. When the two are laid beside each other, the comparison usually becomes straightforward. Where a consultant has made claims about speed or certainty that the official material does not make, that discrepancy is itself important, both for your decision and for anyone later assessing whether an intermediary was acting properly.
Hypothetical example: Aisha, a dental-practice administrator, keeps a promotional flyer but no dated copy of an official program page. She should archive the current government instructions, her processing-fee receipt, the USCIS request for the Gold Card petition materials and any later official gift instructions. Identity and civil records answer different questions from proof that money reached the authorized government recipient. The program’s unrestricted gift is not a private investment and the Gold Card is not a standalone conventional visa classification. A consultant’s flyer or invoice cannot establish the current process, so the official site and agency correspondence should be rechecked before any funds move.