Both are required depending on your surroundings. If you are living among Muslims who need to be nurtured to be better Muslims, you should then focus on that. If you are living among non Muslims who do not know enough about the facts of Islam being the last and final message to all human beings, you need to try to enlighten them and help them know the facts then leave to them to think and decide. No doubt, the reward of enlightening non Muslims is very great, nevertheless,BT he reward if nurturing Muslims to make them better Muslims is also very great.
You can do both as our Prophet Muhammad (SAWA) and his great successors the infallible Imams did. It depends on the need of your surroundings and your abilities.