What is the ruling on sending an invitation to a friend via a mobile message, expressing happiness and worldly supplications not found in the Sunnah?

There is no harm in supplicating with words other than those transmitted (from religious texts), and there is no objection to supplicating for oneself concerning worldly matters. If a person supplicates for another regarding a worldly matter, it is an act of kindness, due to the saying of the Prophet, peace and blessings be upon him: "Whoever does you a favor, recompense him; and if you cannot find anything to recompense him with, then supplicate for him until you think that you have recompensed him."