I recommend to start learning fundamental electronics first then move up to microcontrollers (if you’re interested for that) or straight to device. Make a habit of reading datasheet. Reading datasheet is necessity to understand the characteristic of components you’re after.

While learning Arduinos are good to learn how to handle microcontrollers are interfacing electrics modules. Learning electronics fundamental is good start to put more confident handling electronics (especially low voltage/current stuffs). You may want to tweak lower devices first as higher power devices such as SMPS, Inverter, old CRT TV, Higher power amplifier require more understanding power electronics.

Afterward steps up to analog electronics (op amp, transistors, mosfets) then digital electronics (digital ics, microcontrollers). At this stage reading datasheet is a must in order to not miss anything from components you are going to use.

For learning via youtubes, you can try visit eevblog, GreatScott (general purpose), bigclivedotcom (general device disassembly/tear down), afrotechmods (his old videos are still good for explanation). For books, try to check other commenters.

You can learn at any pace and most importantly have fun :D

source: Am recently graduated mechatronics students, currently working on automotive industry.