Is seeking forgiveness 100 times after prayer with the intention of [gaining] provision and facilitating marriage considered seeking forgiveness for worldly [gain] and a whisper from Satan?

Seeking forgiveness (istighfar) with the intention of achieving a worldly matter is permissible. However, it is more complete for acts of obedience to be performed for the sake of Allah, and any worldly reward resulting from them will follow. Therefore, seek forgiveness and perform your acts of worship as an approach to Allah, and your desire will be fulfilled by Allah's permission.