YouTube University. Seriously: watch 30, 50, or a 100 videos. You will develop an intuition for what is happening.
THEN read books (some good ones already suggested in other comments) and you will learn the concrete theory.
I want to emphasize the importance of developing the intuition behind the theory. It's vital, and the lack of intuition is why so many people find a complex, theoretical topic difficult. If they had spent time developing their intuition, then they would not struggle so much to understand and remember the theory.
Last, you have to build stuff (this also helps with the intuition). Decide that you are going to spend $300, and start buying parts. Don't go to Radio Shack, because you will (in my experience) pay an order of magnitude more for the same part. Shop on Aliexpress (or sometimes Amazon or Ebay). Who cares if you have to wait 6 weeks for the part to come in... do it today and it will be here about the time that you are ready for it. Never buy just one of anything. You can usually buy 10 or 20 for the same price that you can buy 2 or 3.
Most importantly: DO SOMETHING! Anything. Watch videos. Buy parts. Put things together, and then try to figure out why it's not working! Whatever you do, just don't stop. You will learn if you keep at it. At this stage for you, though, the most important thing is that you actually start.
I want to emphasize the importance of developing the intuition behind the theory. It's vital, and the lack of intuition is why so many people find a complex, theoretical topic difficult. If they had spent time developing their intuition, then they would not struggle so much to understand and remember the theory.
Last, you have to build stuff (this also helps with the intuition). Decide that you are going to spend $300, and start buying parts. Don't go to Radio Shack, because you will (in my experience) pay an order of magnitude more for the same part. Shop on Aliexpress (or sometimes Amazon or Ebay). Who cares if you have to wait 6 weeks for the part to come in... do it today and it will be here about the time that you are ready for it. Never buy just one of anything. You can usually buy 10 or 20 for the same price that you can buy 2 or 3.
Most importantly: DO SOMETHING! Anything. Watch videos. Buy parts. Put things together, and then try to figure out why it's not working! Whatever you do, just don't stop. You will learn if you keep at it. At this stage for you, though, the most important thing is that you actually start.