Don't get caught up in understanding too much. You can end up in theory forever because electronics is a bottomless pit of information. Really I'd suggest getting stuck in making kits and then after a while following guides and making your own stuff. The knowledge comes incidentally if you're doing stuff, especially with higher quality kits like Velleman.like what a capacitor actually does and such
Making my IIfx SuperMac'ed and thus @Phipli happy