If you wish to learn to recover precious metals and learn to refine them I suggest you spend a lot of time studying this forum, and read suggested materials.
Recovery and refining of precious metals is an art skill and science, not something you will learn overnight, it can take years of study, and hard work. like many skills that take hard work to learn and practical experience, practicing what you are learning, this skill can be as rewarding as you are willing to work at it to learn it.
I agree with Jimdoc, to give the answer short and sweet to learn this skill:
You need to study this forum.
Maduro,
Welcome to the gold refining forum the best university I know of to learn this valuable skill, if you truly wish to learn this art, and are willing to spend the time studying, about everything you need is here as a resource, this is not something you will learn overnight you can spend several lifetimes and still not learn everything.
I say you do not need any chemicals or supplies yet, you would not know what you really need, or know what to do with it, you need to spend time studying, your chemicals will come as you learn, the processes and ability to find scrap, and how to judge the value will come, your simple lab can grow as you grow in the knowledge, doing anything different at this point would most likely be a waste of money and a loss of values, with educating yourself you will know what you need and when, and will have an understanding of how to use it safely.
So best answer to your question is you need to study the forum.
Follow the links posted above they will help guide you while getting started.