seems like they trying to sell speed lights x)) anyways thier are many other ways of getting light into your scene without spending money. you indoor scenes you can use fixed lighting and for outdoor something large and reflective like a big piece of paper.

Also the easy way to learn how basic lighting works is just look up "three point lighting" that is a classic way of lighting which always looks good from thier you can expand with soft fill lights and rim lights.

for capturing fast motion pictures a flash is what you would use its probley the only time you will ever need a flash as you cant raise exposure and iso values too compensate.

But most of the time a flash is completly pointless and replacable. I would say a tripod is more important in more cases as it allows you raise exposure to high levels without bluring.