A small graph showing which components and modules depend on each other. In small words:

All components and modules need the language class (com_mls_lang) to be installed. Then, most other components depend on com_mls_events (com_mls_seatmap, com_mls_tournaments, com_mls_paypal). com_mls_catering does only depend on com_mls_lang, so it can be used as stand-alone as well. To use com_mls_tournaments, you also need to have com_mls_teams installed.