What's your definition of a good leader? One that can keep a clan solid?
Good is subjective so I can only say what I think is a good leader. A good leader is someone who leads by example, Instead of sitting on their arse and barking orders or what they want to see in players (e.g type in clan chats). The leader will lead by example by doing the stuff. When you see your "leader" or someone you respect doing something or iniating something. A member will follow. Basic sheep psychology right there.
So socially you can be leading.
In the buisness clan sense, You have to try and gain more members then you lose. Growth is important in the players you keep. Member retention is important. Overall, You need to keep all these stable and no major fluctiations in members. For example Outlaws in terms of CL is pretty good. Keeping all their CL main players and are growing internally. Stronger not declining. Growth can be in skill, Community development or simply numbers. It's all subjective and up for personal customisation.
You can divide clan leading into many sub-parts. Every leader will have a strength or weakness in some areas.
Luck doesn't determine if you succeed or not. It determines how fast you will suceed or not. Aslong as you have the right work/attitude you should be continually improving. How much you will be improving can be influenced out of stuff you just simply can't control. All you can do is simply keep doing the right thing. The daily grind ;)