All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
Taking a gradual approach in Da‘wah (calling to Allah) is a genuine prophetic Sunnah. For example, when advising a disbeliever, one begins with calling him to Tawheed (worshiping Allah alone), and then he should be taught the pillars of Islam, starting with the most important and then the less important, as in the hadeeth of Mu‘aath when the Prophet sent him to the people of Yemen. He ordered him to call them to Tawheed first, and then to prayer, and then to zakaah, and so on; this hadeeth was reported by Al-Bukhaari and Muslim.
If the one who is to be advised is a sinning Muslim, then he should be ordered to do the most important pillar and then the less important. If he is not performing the prayer, then we first start by calling him to perform the prayer out of keenness on guiding him and saving him from going astray. If he commits more than one sin and it is possible to forbid him from all of them, then one should forbid him from all of them. Otherwise, one should first forbid him from the most dangerous of them, and so on.
If we know that he will not respond if he is advised to abandon a given sin and he will respond if he is advised regarding other sins, then we should forbid him about that sin regarding which he would respond until we are able to advise him about other sins.
We mean that we should consider the interest of the person who is being advised and observe the best method in calling him and minimize his evil aspects while maximizing his good aspects.
For more benefit, please refer fatwa 65863.
Allah knows best.