Words that seem to jump out of your post.
I would feel more comfortable if I felt dressed appropriately
I’m reading comfort for you would be blending in til you get the feel for the terrain.
I suggest you drop by the class you intend to take, just around dismissal, take a look at what the rest of the zebras are wearing, pick one out with similar stripes to you, and introduce yourself to this post shivasaned bliss and ask her where she got her pants.
Yoga tights were created not just to flatter your a$$ets, and yes you are going to look fabulous, but yoga tights were really created to fit to form, to settle in nicely on all figures, curvy to slim hips, often high waisted to not slip down in some of the rather complicated poses yoga explores, and you can always roll this waist band down. Yoga tights are also going to fit to form to let you and the instructor see from a distance the angle and alignment issues in your postures, for self or suggested adjustments.
You don’t have to trip down to Birmingham, or up to Nashville to check your ethics at the door and drop a Benjamin on getting fitted into some Lululemon pants. As a woman you will have a lot of variety in just about any box store even some of the grocery stores for an economical alternative that will get you by til you feel you can wear whatever feels 'right' in your future.
Maybe that future will even include some ethically sourced clothing, just saying, not judging.
Welcome and enjoy the journey.