I don't know if it is just me but I find Building and Farming skills the most difficult to build to Master level. Perhaps, it is simply because we concentrate more on gaining tech points to proceed in the game. I now have 20 in my tribe with the most inexperienced doing the research while the others are building and farming. When I have my food at a very high level and my bath built I will go back to concentrate on tech points. Already I have four elder plus I am having so much fun!