What should I consider as I design my own workouts?

1. You get the most benefit from the first time you do an exercise / rep. 
2. The next challenge is sticking with it, doing it every week consistently. You can boil it all down to an acronym known as the FITT principle. 
3. The first letter F, stands for frequency, how often you exercise. If you want to continue progressing, you have to be going through a program a few times a week. The second letter I, stands for intensity. The harder you work your muscles, the more effort you're putting in, the more benefits you're going to get from those workouts. Workouts with good effort allow you to gain muscle and get stronger. The final two letters stand for time and type. 
4. Start slow so you don't get hurt, you'll see results and with time, you can do a full exercise plan. But in the beginning you have to just do it. 
5. Only a few supplements actually had evidence sufficient enough to say that they worked. When you go into your local mall or supplements store, there are lots of products that make bold claims. Like branch chain amino acids are fat burners and there's no evidence that they actually work. Even the ones that do work caffeine, creatinine, sodium bicarbonate, protein, and nitrate, only provide a small amount of benefit. Unless you're competing at a college national or professional level, don't bother with supplements. 25 authors across the world who put together a consensus statement called “Dietary Supplements and the High-Performance Athlete.” https://journals.humankinetics.com/doi/full/10.1123/ijsnem.2018-0020