The answer to this question is entirely dependent on the kind of party you’re having and the type of vibe you are trying to create. I think even the most basic birthday party merits renting at least 2 lights, just to set it apart from every other birthday party and make it special.
Are you hosting a large corporate event inside a huge ballroom? If this is the case, I’d recommend renting at least 10-15 lights. One of my favorite uses of uplighting is when the uplighting is set up around the entire room, effectively illuminating all of the walls in the venue. This gives the room a very strong energy as soon as you walk in and immediately sets it apart from the “normal” event. Often times at corporate events there is a keynote speaker – it looks fantastic when uplighting is used to bring guests eyes to the center of attention. Setting up 2 different colored lights (from the ones around the room) on either side of the stage, or podium will let guests know where they should direct their attention, without anyone having to tell them. It also gives the speaker and the stage a level of mysticism and perception that is favorable.
If you are hosting an event inside of a venue that is a little dark, it is a fantastic idea to include uplighting in your event plans. Often times normal incandescent bulbs can give off a weird, white/yellow light, so it is better to have the lights off, right? But then it’s too dark and what do you do? Uplighting is a fantastic way to illuminate a party without overwhelming the party attendants with aggressive white LED lights.