Is it better to reform the conditions of Muslims or to invite non-Muslims to Islam, and is engaging in Dawah an obligation?

Calling to Allah is an obligation upon the Ummah (Muslim community) as a collective duty (fard kifayah), and it is an individual obligation (fard ayn) upon every Muslim according to their ability and knowledge, as the Prophet, peace and blessings be upon him, said: "Convey from me, even if it is a single verse." There should be no disagreement about the priority of calling Muslims versus non-Muslims, for both are required by Islamic law, and each is facilitated for what they were created for. Whoever finds within themselves the zeal and ease in one of the two areas should not criticize the other, for both are good and required.