Time between sets should be short and just long enough so that you are sufficiently recovered to hit the next set hard.
I work out every body part twice a week, and that is what helps me stay in shape.
I am not a trainer, hence I cannot advise youngsters on the use of supplements or the way to build their bodies. But I can tell them one thing that I did - find a good, honest trainer.
My supplements are similar to my training - I always commit to being a better version of myself.
I learned the ins and outs of the supplements business as a bodybuilder. I'd worked with some of the companies, and I knew a lot about the products. Some of them worked OK, and some of them didn't. I wanted all of them to work, not just for me, but for other people, too.
Knowledge is the real power.