A gaming system is disclosed that comprises a symbol selector configured to select a plurality of base symbols from a set of base symbols for display in a display area; and at least one set of additional symbols, each set of additional symbols including a plurality of additional symbols. The gaming system is configured to incorporate the additional symbols of an additional symbol set into the base symbol set so as to define a combined symbol set, and the gaming system is configured to select and display a plurality of base and/or additional symbols from the combined symbol set. The gaming system further comprises an outcome evaluator configured to determine a game outcome based on the selected base and/or additional symbols.