Seek forgiveness three times
Arabic: أَسْتَغْفِرُ اللَّهَ
Transliteration: Astaghfirullah.
Meaning: I seek Allah’s forgiveness.
Allah is the source of peace
Arabic: اللَّهُمَّ أَنْتَ السَّلَامُ وَمِنْكَ السَّلَامُ تَبَارَكْتَ يَا ذَا الْجَلَالِ وَالْإِكْرَامِ
Transliteration: Allahumma Antas-Salamu wa minkas-salam, tabarakta ya Dhal-Jalali wal-Ikram.
Meaning: O Allah, You are Peace and from You comes peace. Blessed are You, Possessor of majesty and honour. Reported in Sahih Muslim.
Tasbih after prayer
Say SubhanAllah 33 times, Alhamdulillah 33 times and Allahu Akbar 33 times, then complete one hundred with:
Arabic: لَا إِلَهَ إِلَّا اللَّهُ وَحْدَهُ لَا شَرِيكَ لَهُ، لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ وَهُوَ عَلَى كُلِّ شَيْءٍ قَدِيرٌ
Meaning: None has the right to be worshipped except Allah alone, without partner. His is the dominion and praise, and He has power over all things. Reported in Sahih Muslim.
Personal dua
You may ask Allah sincerely for goodness, guidance and forgiveness. Learn the established adhkar without treating one valid reported form as the only permissible form.