Identity and civil documents for everyone included, a clean record of prior U.S. travel and any refusals, evidence of the funds that will make the gift, a saved copy of the official terms as read that day, and the questions to be answered before the fee is paid.
Which document decides it
The document that governs is the official programme page on the day of application, because its terms have already been restated since launch and any secondary summary may be out of date. Save a dated copy. Hypothetical example: a Lévis manufacturing founder reads a broker's brochure that quotes a gift figure and family terms from an earlier version of the page, prepares a budget on it, and only discovers the change when the fee invoice arrives.
Beside the official terms, gather passports, marriage and birth certificates, prior visa records, and the bank and sale documents showing where the gift money comes from, since vetting will look at the source of funds even though the money is a gift rather than an investment. Follow the official instructions for whatever USCIS forms and evidence are requested after the initial step; a file prepared for EB-5 cannot simply be relabelled, because it proves job creation and at-risk capital, neither of which this framework asks about.