To dream of groups can indicate you are to work with groups as a spiritual leader / teacher. Spiritual teachers empower others rather than taking their problems away from them. Look for other symbols in the dream that indicate leadership such as a leader, instructor or someone talking with authority.
Groups can also be indicative of your body being packed with waste food. In this case look for other symbols that indicate the dream is about your digestive system, such as references to eating, food, tables, kitchens or bathrooms.
Lastly groups crowded in large rooms can be indicative of breathing problems.