Can you promise plenty of group activities? One huge reason why clans fail is because they rarely do anything together. You should do a group event already every week, if not more.
Also, how to you decide who leads or if someone leads? Is it seniority, skill, all equal, or another method?
What is your goal as a clan. Not the clan goal, but what you want the clan to become/do.
Lastly, if you only want good builders, that's not his you can get quality people in your group. Many people specialize in scripts, or quests, or something else, and if you ask for good builders, it takes that small bit of people who "can" build and cuts that down to probably 5% of total miner players. I say "can" because its just a matter of opinion. I always say that if you like what you build, then its perfect, many people I've met say they suck at building and I love their stuff. If you judge someone's builds, you will be saying that either its good enough for your standards, or you don't like it, so they don't pass. You should consider open joining, I've met new players that I've taught to be a good builder. I gave them a chance because they asked for help, and they are now amazing at what they do.