If you've been experimenting with Flash photography, you might start to gain interest in light modifiers. With different types of modifiers you can shape the light and target exactly where you want it to be. I know some guys who carry between 4-8 speedlite flashes (or more) when on assignment. My favorite modifiers for small speedlites are honeycomb grids or snoots. These create a somewhat spotlight effect perfect for hair, rim lighting, or background seperation.
If you're running around at an event, the most common modifier is the large diffuser. So that you aren't casting harsh shadows, you'll need a Stofen, Light Sphere, or Globe. Here's a great kit for a great price and even comes with a set of colored diffusing panels. We often use colored Gels over speedlites, but these colored diffusers seem to work in the same way allowing you to add different colors to the background without having to change out the whole roll. The video seems outdated with the $100 dollar price tag, as they can be found much cheaper now.
Flash Kit Softbox, Colored diffusers, Snoot, Grid, Globe, Barndoors, and more