No worries at all. You can use PVA, it is v cheap after all. I would normally suggest something else for a beginner though.
I would still put some paint down when you do a dirty pour, even of you only pour a ring of paint around the mouth of the cup once it's upside down on the canvas. It aids enormously as it helps the paint to move around the canvas. If you use a dry canvas then I would probably use much more paint (in the cup) than you actually need. Not sure if that makes sense.
The videos do make it looks really easy and as you've said, it isn't. There is a certain amount of luck involved but it's like making a cake really, if the basic ingredients aren't there, it won't work.
I would sort a few things first:
prepare /cover your work table so that clearing up is easy and you're not concerned with drips or splashes of paint. I'd also cover the floor around the table.
Mix your paints before you start pouring, let them sit for a while.
Have them lined up ready to use. Have wipes/kitchen roll/disposable gloves ready.
Prepare your canvas ie a layer of gesso if necessary.
Be aware that if you don't use enough paint, the end result will be rubbish. For example, if you're eeking out the paint and trying to pour it over all of the canvas and just about manage to move it to the edges, it will shrink. You'll be left with no paint along the edges of the canvas.
If your paint is too thick, it will crack once dry and ruin the end result.
Use masking tape or frog tape on the back of the canvas as well as large flat headed drawing pins (the canvases will then stand and the paint can drip off).
Make sure that your work area is flat ie I use a spirit level. Your paint / picture will be ruined if not as the paint runs off down one side!
Catch/wipe off the paint that has dripped off - if you don't, the weight of it will pull the paint off from the middle of your finished design. You can use a palette knife to sweep round the underside of the canvas.
HTH