Learn how to base your clothing style around your style of workout.
If you constantly like switching your workouts up with some runs, yoga classes, circuit training, and weightlifting, then you should think about letting your exercise of choice mandate your style. You want your apparel to help you move while keeping everything in place, not hindering your form or distracting you from the workout at hand.
I have put together a sample outfit to go together with each of the following workouts. You can use this as a baseline so that you have a better idea of which outfit styles work best with which exercise stye.
Cardio and high intensity interval training involve both lateral and vertical movement. Whether you are running, squat jumping, or going for those burpees, you want to choose an outfit that stays in place and keeps you in place as well. You can choose the same kinds of tops and bottoms for both cardio and HIIT, but your shoe choice will differ. That's why I listed an example of a form-fitting outfit below with a cross-training shoe as well as a running shoe to pair with it.
A yoga or pilates class will not involve a lot of jumping, so you don't need the highly-supportive sports bra. But, you will most likely flow down to the mat and back up again throughout the class, so choose a top that won't fall over your eyes when you bend down. You will also want comfortable, breathable leggings that you can bend and stretch in.
While you will definitely sweat at the gym, weightlifting usually works in slow, controlled movements. This means you have a little bit more freedom in your clothing choices. Leg day will cause more sweat than any upper body day, so do think about your legging choice before hitting up the squat racks. Choose a thick enough pair of leggings that won't show your sweat or something more when you bend down for squats. When doing upper body work, I like to wear a tank top so that I can double check my form in the mirror and make I'm working the right muscles.
