I've found that 3 types of supplements help my workouts. Here they are:
1 - Pre Workouts
Pre workout supplements really help your focus and your performance in the gym. I like stimulant based pre workouts, but there are plenty on non-stimulant products that work wonders as well!
2 - Ergogenic Aids
Ergogenic aids are daily supplements that can boost performance and improve body composition when taken properly. Things like Creatine fall into this category. Sometimes you can find pre workouts with ergogenic ingredients already included for ease of use.
3 - Recovery Supplements
These indirectly improve your workouts due to less soreness and better overall recovery from previous workouts. The better recovery means more energy and potential for future workouts!