Start with this Du'a
After wudu
أَشْهَدُ أَنْ لَا إِلَٰهَ إِلَّا اللَّهُ وَحْدَهُ لَا شَرِيكَ لَهُ، وَأَشْهَدُ أَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ. اللَّهُمَّ اجْعَلْنِي مِنَ التَّوَّابِينَ وَاجْعَلْنِي مِنَ الْمُتَطَهِّرِينَ
Ash-hadu an la ilaha illa-llahu wahdahu la sharika lah, wa ash-hadu anna Muhammadan 'abduhu wa rasuluh. Allahumma-j'alni mina-t-tawwabina wa-j'alni mina-l-mutatahhirin.
“I bear witness there is no god but Allah alone, with no partner, and I bear witness that Muhammad is His servant and messenger. O Allah, make me among those who turn to You in repentance, and make me among those who purify themselves.”
Sahih Muslim 234, Jami at-Tirmidhi 55 (sahih)
The Prophet ﷺ said whoever completes their wudu and says this, the eight gates of paradise are opened for them.