Upgrade your troop tunnel to level 11

 One of the clan requirements is that you upgrade your troop tunnel to at least level 11. This will give you four slots in the rallies for lizards and event creatures. It benefits both you and the clan.

You will need Refined Sand to upgrade the tunnel. You can buy it for diamonds. Note that buying in bulk gives the best price per item.

If your Lady Bug is at lv 13 or higher you will also find offers on the Refined Sand from time to time, these will always be cheaper. But don't wait on these if your troop tunnel is not on lv 11 yet, getting there has priority.