The material composition that you will like really depends on what your goals are.
Personally, my favorite blend of materials is always ~81% Nylon & ~19% Spandex.
My favorite leggings have the following material compositions:
W227 - CURVE FLARE LEGGINGS: by YoungLA (81% Nylon, 19% Spandex/Elastane)
FOXY FLARE LEGGING: by BuffBunny (74% Nylon, 26% Spandex/Elastane)
SUNZEL FLARE LEGGINGS, CROSSOVER YOGA PANTS WITH TUMMY CONTROL, HIGH-WAISTED AND WIDE LEG: by Amazon (80% Nylon, 20% Spandex/Elastane)
OFFLINE REAL ME HIGH WAISTED CROSSOVER SUPER FLARE LEGGING: by Aerie (88% Nylon, 12% Elastane/Spandex)
That blend gives a buttery-soft feel without being too compressive. It is also a common blend for athleisure wear which makes it comfortable to lounge in but also do light workouts/weight-lifting if I want to.
If you want a buttery-soft “second skin” feel, I suggest looking for descriptions like “double brushed”, “breathable”, and “super stretchy”.
If you’re looking for extreme stretch, go for blends that have a higher percentage of spandex (also known as Lycra or elastane). Spandex stretches up to 8 times its usual size, so you’ll get unrestricted and comfortable motion in any activity you do. The downside? Higher spandex blends can have less moisture wicking properties. They can also add a sheen to your clothing depending on the quality used which can make clothes look cheap.
If you’re looking for softer fabrics, go with a higher Nylon composition. Nylon is soft, stretchy, and sweat resistant. The downside? Nylon is not nearly as stretchy as spandex, so it can be slightly more restrictive.