For the Friday prayer, is it sufficient if one takes ordinary bath (without Wudu), or is it compulsory to make Ghusl (ritual bath, starting with Wudu ...)? Please advise.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Performing Ghusl (a ritual bath) after sexual defilement, or after the end of menstruation, or after post partum bleeding is sufficient and one is not required to perform ablution. Ibn Qudaamah, may, Allaah have mercy on them, said: 'Ibn 'Abdul-Barr, may, Allaah have mercy on them, said: “If a person performs a ritual bath after sexual defilement without having performed ablution and he poured the water over all his body, then he has indeed done what is required of him as Allaah ordained him to perform a ritual bath after sexual defilement but did not ordain him to perform ablution.'  Al-Kharashi from the Maaliki school said: 'It is sufficient to make the intention for performing a ritual bath after sexual defilement, or after menstruation, or after post partum bleeding, instead of making the intention for performing ablution.'

As regards Friday Ghusl, ablution has to be performed before the bath or after it. As-Saawi from the Maaliki school, said: 'If performing Ghusl in not an obligation, like Friday Ghusl, or Ghusl for ‘Eed days, then even if he intends Ghusl and ablution, that is not sufficient of him, he still has to perform ablution when he wants to perform the prayer.' 

Allaah Knows best.