NO CHANCE...
Just now personally Checked
Delhi to gaya ,
And Delhi to Patna-Gaya ,
And Delhi to Varanasi/Mughalsarai-gaya...
All...
more... three routes are completely Jam Packed...Even the Premium Tatkal is also full....Its summer vacations time...Very difficult..
Ask him to book tomorrow's tatkal or Premium Tatkal for 25th departing train.
tell him prefer booking in 12816 (Ttakal & Premium tatkal also) , 22806 (Tatkal) or 12818 (Tatkal).
These 3 have chances of giving confirm seats. Or else Mahabodhi or poorva is just out if question.