Summary

You built twelve 74-series chips from transistors and a dice on them.

A package — several identical gates and pins with numbers and names. Free inputs go to ground.
A flip-flop in a package — the 74HC74: clock, data, set and reset; two make a divider and a counter.
A counter — the 74HC390: ÷2 and ÷5, together ÷10; the second half is the tens.
A decoder — the 74HC138: a number chooses one wire; two make 16 wires.
A shift register — the 74HC595: a byte over one wire and a latch that shows it at once.
A bus — the 74HC244 and 74HC245: the third state, only one talks.
The dice — a counter to six and four wires for the dots.

Twelve chips — 1,448 transistors.

A different counter. Replace the Johnson counter with the lesson 2 divider and a reset at six — and compare how many gates it takes.
Two dice. A second counter on a free flip-flop with its own clock — and the dice fall independently.
New chips. The catalogue has hundreds: the 74HC161 is a binary counter, the 74HC283 an adder, the 74HC4511 a decoder for a seven-segment digit. Each can be built the same way: from the datasheet, out of the ones you already have.