I think the thing with video is that you want consistency... And that can be pretty hard/expensive to achieve. Getting a good LUT will take a major step out of that. Free LUTs tend to just be er... a skin I suppose. Something that may/may not work for your scene/camera etc. Buying something like the Leeming LUT will, assuming you have the right camera and set it up correctly, take you to a reference colour space that you can then work from. It also comes with 'quickies', second set of LUTs that will give you various creative effects.
Making your own LUTs looks like a proper rabbit hole. I think Gerald there has some guides on it. I mean amateurs obviously do do it, and do it well... But I think when you're just starting out, and assuming you're doing the full edit yourself, having a decent LUT to work with is going to let you spend more time filming, getting the cut right, working on effects etc.