^^As Mike said.
You mentioned that you had several non-functioning kits that you assembled, correct? Well, get your multmeter and startout by trying to fix them so they do work. Good troubleshooting practice, you have the schematics I'm sure, and you can ask for assistance on here. There is nothing better than trying to figure out your own mistakes.
Chris
I agree with both this post & Mike's.
Making kits saying,"That doesn't work!",& chucking them in the junk box is not the way to learn.
Learn how to read schematics ,if you don't already know how,become familiar with component colour codes,& approach the thing as an
Electronic circuit.not as a "kit" that you build "by numbers".
Pulling Commercially made stuff apart gives you an insight into how things are put together in the real world.
Reputable Manufacturers will often make components & PCB tracks larger than strictly necessary in power circuits,whereas others do stupid things like using undersized components & tracks---you'll recognise them by the burnt bits!!
I would advise against trying to design things until you have built
& understood a few examples of other people's designs.("Zombie" type construction doesn't make it!)
This is a common mistake by beginners on this forum.
They see other members designing things,who have either years of experience as Techs or EEs ,or are well into their Uni EE course & think they should be able to do the same,although they have very little theoretical knowledge.
Breadboards!---- I hate 'em!
But that's just me,& I'm a grumpy old sod!