Recessed light fixtures can be a major source of heat loss, but you need to be careful how close you place insulation next to a fixture unless it is marked. "I.C."—designed for direct insulation contact. Check your local building codes for recommendations.
Set the fan on your central air conditioner to “on” rather than “auto.” This will circulate air continuously, keeping the temperature more even throughout the house and aiding in dehumidification.