After finishing all purple walls, I’m doing skulls now. Its not important to max skulls at all, but I prefer having around 50 of them when I reach TH9. As a new TH9, elixir demands are so high that one can easily do half skull walls while working on those upgrades.
Having only 170 training capacity while having 200 camp space is quite hellish. Can’t wait to max at least 2 of these barracks