I bought a blueprint, but...

[Luna plays]

...how do I unlock it now please?

[Winter's Embers]

Happiness no longer has any effect on the game at the moment so you should not be using the emoji sliders. Keep them at orange level to keep needs manageable.
End game (more than 40 population) isn't introduced yet. There are a number of buildings and other gameplay elements that will need to be added to the game before end-game becomes possible. For now, keeping the population below 40 is recommended until you fully understand the complexities of large-scale production. It isn't easy, believe me, because Needs amount per item is still too small for available items.
Clay will remain as a Need because there are indications that it will be a primary component in building foundations and walls. There are certain unlock announcements you may see during the early levels to show this. The problem isn't the clay, it's the lack of a priority system in Needs consumption which is still a primary focus of the development. When that is worked out (and I can't imagine it is anything but really damn hard), the Needs consumption will be far more manageable. For now, you just have to keep Clay out of the General Storage building to prevent its consumption. Using a shed or other decorative container that was introduced in this update is the best way to keep clay. Also, keeping your storage inventories managed by moving required items to the top each and every season is the best way to manage what your people consume. Remember, it is first-come, first-served so whatever is placed first (top-left box and moving right across the row before moving down) will be consumed first. Doing this every season can be tedious, sure, but it's the only current way.