I responded to your other topic as well and definitely echo what Rob pointed out. I have never, and never will, limit myself to only a few kinds of thread let alone just stick with one fiber type. Like Rob, I choose my thread for the look I am going for and what suits the type of quilting as well as the quilt best. Like Rob, I rarely use cotton threads due to the lint issues but I won't hesitate to use a cotton if the color is perfect. Variegated threads I tend to only use in pantos or continuous designs where I won't be backtracking over previous quilting. It is not uncommon for me to use numerous thread types and colors in a single quilt. Here are links to pictures I have posted before and I usually talk about the thread in my posts. This one has 5 different types of threads used in it and each kind of thread used multiple colors (except the monofilament):
https://www.quiltingboard.com/pictures-f5/quan-yin-show-quilt-t297585.html
Thread can do so much more than simply hold your layers together. It can become a decorative element all on its own like in these quilts:
https://www.quiltingboard.com/pictures-f5/peony-fantasy-asian-panel-quilt-massively-quilted-t302441.html
https://www.quiltingboard.com/pictures-f5/agave-garden-big-reveal-t270708.html
Here is an example of using King Tut variegated with a panto:
https://www.quiltingboard.com/pictures-f5/retirement-quilt-coworker-t293700.html
And this one I used all invisifil when I was first experimenting with that thread (I used a sampler package that had 5 small spools in different colors but same tonal family)
https://www.quiltingboard.com/pictures-f5/batik-block-swap-quilt-t221823.html
My best advice to you is to not stock up on a bunch of thread until you know what style you like to quilt and what threads you like best to work with. Many a novice longarmer has made that mistake and often end up with cones and cones of threads they either don't like to use anymore or never truly loved in the first place, myself included. If you want to get threads while you are in the states, perhaps you should get a wide assortment. I would suggest getting the following assortments to get you started:
A monofiliment thread. Used for ditching. Superior Monopoly is a polyester monofiliment and Glide essence is a nylon. With a thread net (cones of this thread usually come with one) I have had great success with both.
A trilobal 40 wt polyester thread. Usually very shiny in appearance and a vast array of colors. A strong thread that is not subject to weakening over time like a cotton can. Brands I have used are Glide and Isacord. Both Superior and Wonderfil (which happens to be a Canadian company so you should be able to get easily in Canada) make one but I haven't tried either. Superior's brand is called Magnifico and Wonderfils is called Masterquilter.
Speaking of wonderfil, they make many oh so awesome and beautiful threads. I positively love their Invisifil and decobob. Both polyester. As Rob said, the Invisifil handles and looks like silk, very fine and also a great alternative to monofiliment for ditching as it sinks right down into the fabric so all you see is texture not thread. It is 100 wt. Decobob is very similar and it is an 80 wt.
Their specialty threads are also fabulous. I have had great luck with their metallics and I do use many of their heavier threads for hand work (couching, hand embroidery, decorative stitching and sashiko)
From Superior, I think you should get at least one cone of King Tut to see how you like it, this would be a good option for one of the smaller "try me" spools they offer. Of all the cottons, this is by far the nicest I have used (and I have used several brands in my machine, YLI, Essential cotton, Aurifil to name a few) and King Tut produces the least amount of lint and is really strong.
I also like some of superior's specialty threads like their metallic and Glitter, their holographic thread and Kimono their 100 wt silk thread. But I tend to use invisifil much more due to the cost of silk.
Don't limit yourself to just one type/fiber/brand/style of thread. I have to admit my thread addiction is equal to my fabric addiction. [SUB][SUP]