The answer to 'what size lighting installation do I need' is the size of your lighting installation depends on the size and layout of the room, the type of lighting fixtures you want to use, and the overall lighting needs of the space. As a general guideline, you'll want to have 30-50 watts of lighting per square foot of the room.
For example, a 10x12 foot bedroom would need 3,600-6,000 watts of total lighting. This could be achieved with a combination of recessed lights, wall sconces, and a central overhead fixture. The exact fixture types and wattages will depend on your personal preferences and the desired ambiance. It's always a good idea to consult with a professional electrician to ensure your lighting installation is properly sized and installed safely.