I think answering that depends on ones goals and current level of understanding. Some others in the other thread did a good job pointing in the right direction. Whatever gets you away from just watching Youtube and actually building basic circuits. Adafruit has some good starting points, or used to. If you can hook up an op-amp IC and get it to amplify a signal and why that works intuitively you will have gotten pretty far. Really, the intuition comes from understanding what frequencies capacitors and inductors help and hinder, and what happens to components in parallel and in series. Build a radio kits used to be pretty awesome for this.