Your Clan levels up when your Clan members’ collective contributions reach a certain level overall. You (or your Clan-mates) can get contributions for doing bounty quests, doing faction events, donating mystery crystals, finishing daily quests, etc. It’s likely that you’ll reach a decent level eventually, since if you’re even slightly active you will get some contributions added each day. At present, reaching around Clan level 3 can be useful because of the Dragon Mirage Realm event. However, the events for levels higher than that aren’t particularly useful, so that doesn’t matter that much at the moment. There might be further events added in the future for higher levels.