Gymshark has become the default recommendation for women's gymwear for good reason — the Flex leggings use a seamless ribbed construction that moves without restriction, a high waist that stays put during any movement, and a fabric weight that's opaque under any lighting condition. Available in a range of colours, built for performance rather than just aesthetics.
Alo Yoga makes the gymwear that professionals and serious practitioners wear — the Airlift fabric is proprietary and provides compression and smoothing without the restriction that cheaper fabrics produce. The high waist is properly high, the seaming is flattering across all figures, and the fabric holds its shape and colour through serious washing cycles over years of use.
Lululemon's Align legging is the one that most other brands are trying to make. The Nulu fabric is so soft it's been described as a second skin — weightless, sweat-wicking, and four-way stretch that moves exactly as you do without pulling down or bunching up. The high rise stays at the waist through any movement. The legging that converts people who've never spent this on gymwear before.