some of us, (myself included) are occasionally delusional enough to assume we can do it better ourselves than acquiring those products through commercially available sources. With that said I have purchased perfect sets from both Cath and Teresa.
Which products do you want?
Cath has Skybond: It is super slippery, thinner diameter, but a softer hand. Teresa sells LaserPro which is more commonly used with most team quad fliers..., not as slippery, thicker too, but also much more like flying on wire. A direct connect? When you do 3D stuff, the LPG string doesn't pick-up debris as easily or tangle as quickly (or as tightly!)
I use both brands, depending on the circumstances presented and who's with me. I particularly like the 50# and 140# Skybond though for tough conditions (one's for each end of the wind range), but for seriously chasing spectators the line is 90#LPG, especially when throwing the kite all around with tons of slack in between movements.
Some of my linesets have sleeving, but only if I bought 'em that way.
When making my own lines that is just another darn thing to tangle-up which is eliminated by design. Use figure of eight knots, but first place a stopper knot into the single strand line before it's formed into the loop. Practice the figure of eight knot as it wants to tighten in both directions (towards the knot's center point) How do you predict where it will wind up? In fact you'll use a set of forceps to pinch the two strands together where you want the knot to be as a final location. When you practice tying this knot, you'll need to identify the two loops (which resemble an "8" on it's side when visually examined). You have to force one loop OVER the other half and pull out all of that accompanying slack back out (away from the locked point) so the knot positions itself against the forcep jaws as a final position when tight. This isn't easy, you'll have to wiggle and work it, so practice.
When you make linesets without sleeving you need a BIGger loop than with sleeving, as any adjustments will be made by shortening the longest line (by adding in still more knots). With sleeving you can untie, that won't work w/o it!