What I would do is seperate your pattern into a top and bottom half.
The top half of the pattern is perfectly usable as it looks like a similar construction. For the bottom drapey half, I would not attempt to use the pattern, as it is complicated for someone who isn't on a machine regularly. Instead I would make something more like the picture. It'll be easier than you think (and a lot easier than that pattern!)
The picture you like shows gathered drapes going all the way round the hoop with the openings tied back. All this is is a two large rectangles of fabric, sewn together wrong sides out then turned right way out (so the fabric pattern is uppermost both inside and out).
Then I would follow the pattern instructions to attach the simple rectangle to the top half of your pattern. I presume this involves some sort of hula hoop.
Material measure: All you need to do is make sure that the long edge of your rectangle goes round the hula-hoop ideally at least twice, so you can gather the fabric rectangle before attaching it to the top half. The gathering creates "puffiness" and room in the tent (see your pic of the expensive one) otherwise you will be making just a hanging tube!
Make sure your length is nice and long for the fabric rectangle so it drapes on the floor a bit. More drape is better than less.
Width: Measure the circumference of the hula hoop. Your fabric will need to be at least twice this for the width.
Height: Measure the drop from where you will hang it (for kids, I would think the drapes section start at around maybe 5' length plus an extra 2' for where it drapes on the floor, if desired. In this case that's 7 feet height. You may need to join two lengths of fabric together to get the rectangle size you want. This can be made into a feature if you mix and match wide strips of different patterned fabric. Don't forget you will need to times the fabric rectangle requirement by 2, for inside and outside layers.
Finally, to create the openings, sew a length of ribbon approx 20" from each open end, then a corresponding ribbon on the opening itself. You can then tie the openings back.
Give it a go. Don't get bogged down with that complicated pattern.
PS. For this sort of project I completely ignore any arrows showing direction of pattern laying on the fabric. It really doesn't matter, unless you are following the fabric's own pattern and trying to get pieces to match up from an aesthetic POV. Other than that it's to do with drape and grain, usually essential to do in dressmaking but definitely not in drapey play toys (IMHO). Waste of fabric!