If you really want to learn digital electronics you should learn how to design a very simple CPU from scratch. If you can do that then you can build virtually any digital circuit you can think of. And it is not that hard (although it will take some dedication, months of reading and experimenting) Plenty of resources out there that teach you how to do it from scratch.
When I was a kid I tried to learn electronics by buying these types of kits. They were totally useless, complete waste of money and they only accomplished in making me feel that electronics was way too hard for me. All I could do was assemble the circuits in the diagrams but there was no understanding involved.
The worst part was that they all used some computers chips, like the 555 timer, to do some special effects, etc. When you are starting out any chip is kind of useless in your goal to understanding digital electronics.