This is a "Who Has NOT" reporting requirement, which is the primary use case for Cross Filters in Salesforce.

How to build this report:

Base Report: Create a report of Contacts (or "Contacts with Opportunities").

Annual Fund Filter: Set the standard report filters to show only those who have $0 in giving for the current year.

The Exclusion (Cross Filter): Click the "Filters" dropdown and select Add Cross Filter.

Configuration: * Set the filter to: Contacts WITHOUT Campaign Members.

Add a sub-filter to the cross filter: Campaign Name EQUALS [Upcoming Gala Name].

Result: The report will now list only people who are donors but are not currently registered for the Gala.

Why other options are incorrect:

Filter Logic (Option A): This is used for "AND/OR" statements between existing fields (e.g., 1 AND (2 OR 3)). It cannot easily look "across" to the Campaign Member object to check for the absence of a record.

Summary Formula (Option C) and Bucket Field (Option D): These are used for calculating or grouping data that is present in the report; they cannot be used to exclude records based on their relationship to other objects.