The task you have set before you are these main items:

  * create a sequence 8 counts long
  * convert the sequence number to a 7-segment display

The first part is a 4-bit counter that resets itself on count = 8. Easy enough.

The rest of it can be done a couple of ways.

  * Easy way: use a 4-bit out lookup table for the digits, then use a 4-line to 7-segment decoder
  * Hard(er) way: use a 7-bit out lookup table.
  * Hard(est) way: express each segment with a Sum of Products expression

I've rendered the 'easy' way below ([simulate it here][1])

[![enter image description here][2]][2]

What I've done is used four 8:1 multiplexers plus a 'special case' 2:1 for count=8. A little trick to allow using smaller muxes, but of course you could use 16:1 types.

To do direct encoding of 7-segment you'd add 3 more multiplexers and set them up with the digit segment tables.

To do Sum Of Products form you'd replace the seven multiplexers with seven AND-OR arrays, one for each segment. You would wire up AND terms for each segment-lit case then OR them together.

  [1]: https://falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWEAmAzNALAdkggnMmAGxFYKSpLkhIao0CmAtGGAFBgJJMAckNRfkyIYB-cRy4he-VD1HDRc0RM7c%20ILKiLSRm7VCiT1-ZJB67RZixIDu4HVp16nR%20y4N6iPG23ejvCyY8Zx83aWQEUKDIxzNwlmQLVxl9HUhJBWRkUSihMCSxQ2RDBD9pAos86Q1qjPtiIr068ubBEGaC8M6SpliaLvqIqIHe-oQMFXK%20kYmsnJpJhOzcrB0ZnQQ15dntjY6wof3A6RCD33tU-F7WEuuE25oCCq61i5eSt5r%20L6PH%205YXQwjT%20QMaqWB6Wmj0hHxQGDscJyQg0yKMACVhjoeOCkhYcToICUwHAUNAkMhyYYYGVLo8CXDftMNMoKoVWUNGqy9BzWkp5B0lAYhjyDPtUMLpv0Jetpd4djptDEFkqFZp4n0wlh4kcViAEUJ%20gajJx5vyFJUQByUKVJIbtaMIg7YaZbZcjaS%20s7SbrvfaSi6pWEEF1NckdXanSVUBrkA69a7%20LSo-rPXjU4iwxmImEY5m4yU9V7C%20ZlvHS6lrOFGlW9FWRQEwsR%20CdOe0QyUetX2jLBVbJQ12rWrKXdSNtYaFhPuiOLHowEsG%20Alkw88uppc1wuFGuyCUjruEGMp0e1b3xRHOPQ%20lOxZbXK6qNCugz9gyhrDUJBRLDW%20Vf027R-vYOBKN%20mjgcBEGNhYAHvHgzxfqICGdoc5Qoec0GYZySQtmEGFQZUsjgUR2HlM2jqTFUgz-hg1EBnRVrgUMrgdmkTEbvqjFsaxNENJACxsSSKrMeUvHEgJuR8eAqBdEJsnRqJ-GCV0YAKY6bayAYdFaVC9g6f2OgGUh4RfL2ZlKfqLIGGZA6aPKvYkiMvacrgioGE5iqWZ5hkyUsLnkag-keUFYFTGAAqUMSRmNCCVocAKIj8I0oEOIYqAJchhSNBhcUZRFogFLFhK4WlsjlEeQT-Nlek0DVjoguUDKNHwyW1a%209LFdWJKFYS5gWI1DQ9XCrAkbVanPLFqDbINMnPICxKoJN41DqWFGpBkAAyVqniy8QaMlIAAGYAIYADYAM4MDQRjbVF4BdFugyGKdl3XUgW07cS-nxNu1LHedV03Z991gNsW7bOIANvcDbB3aeVZrvWL2A%209t1ffCsjxGiUOvUDH1wxjXK-ek4DQ-j6P3Yxa6MbjqOw9tSVWR0pa0yjMME4zCJpYIA2kxAeNo59TNorzmP-YLDOCqYpZi8j-CS5z0vgNsYtg6TCv00rTN-Wri7sxTwvc48avPZrHPo0zGhiwdZOKyaWwdA6wiljwMa6KOmjUhweBYDQeywqlTC-tuhMEPi-A8Gctvm4bYfZS%20ZyPHTFufeH64gFHhL6wLWvo%20n6uZ0nkMG0L8cWFWWcoJ7uep%20X4tVzjpdSwX2JJ-z5Nl9t6eMVXbOx134CENiyUFZnUO13H21FYSqlj8nzdKzPGesAKf0p1PQ%20xTN88l5Pg-L1Wq%20zoY%209S4fxtj03A-n8PaXH2Vdt559y%20MQ-bNnwTY90Dc2wGSw2wsDEAGpldU%20RAHygAY4YB4BQEkgrIXHyUDNAwPYPPZAZxkFqRXIXIB8p2DbQwJgmEegFoS2foTLAAoyF7jhBvA%20kBnaPB6vkM2ndz7aFYYtQoZDDr2w-O7ZBsJkEfnBIXYRB1-zgg0EHSRIFwKpCDoXFiGpcEKOUeROAVVtgYREeheaGhdEaPkQoQxBjEQFGITNUqeiGg2I0KRWxIBdEOPsYiCRbUUSIlatIAyPjg60zEpAqi9kggGRYmKEJKRwmtArCEsWLt3gJLFqQXoYsRTOy2M4bmTAskziEHkpmASkmZKWEQEYuTFytAqXMDoFSMB6BFPUrwzsQkZN6GxVJvi5FO16AZIObTYlBDXAk9MIoKzpkqhEUcfIhAjJyWM2ZOZ8S4hme4Z2IyNmWS6auEiw0%20hrKwquX6S0xgzIAB4oAmCgegyB5R3P1PCEAAAxNglzIj0CkHczYsEnnsHeaeK%205TwA8D9lYQqbyrn0B4BSHAmdfkLAACKQsiIVCKKBSBb0eQsDIALwUUkxTkBFUw8XgGoHcv2V5sVWBRdcu%20FKUBgDwNS%20KAL1gkh0Hc5lLAKAsvYAAIxueyjBMk9h4F8IKtA3AIBFSQF%20IwkrKBWhlYQJARB9xsEVWqwqqrnEE0VToPASBl4FChIqylcYt6UoQBKm51rmVFUpXgCQiqBpRy3hXCMkrubZBVdjU8GQgA
  [2]: https://i.sstatic.net/m41ie.png