Building counters with flip-flops is not hard but easy. Then I show you a few counters that they count from 0-3, 0-4, 0-5, 0-6, 0-7, and two more from 0-9.

Step 1: Counter 0-3

This counter shows its schematic, plot of work, and equations. Note that it's only 2 flip-flops.

Step 2: Counter 0-4

This counter shows the same elements than the counter 0-3 but note that this needs 3 flip-flops for working.

Step 3: Counter 0-5

This counter also needs 3 flip-flops for working.

Step 4: Counter 0-6

Counter 0-6 is also a 3 flip-flop counter.

Step 5: Counter 0-7

You can realize counters from 0-4,......0-7 need 3 flip-flops for working and doing its sequential logic correctly.

Step 6: Counter 0-9

Counter 0-9 built with T-flip-flops and JK-flip-flops the fist and the second respectively and same also needs 4-flop-flop for working of right way.