Should I start an alliance or join one?

I would go for join an alliance every time! Being the boss of an alliance is a lot of work, in the beginning you have to attract people, then you have to know the game inside out and be prepared to spend a lot of time on it to for wars, for discussions with other alliances etc... A lot easier to join an active alliance and be a player, then if you want some extra power, apply for one of the ranked positions.