Sometimes it is possible to get cheaper solutions by having a look at limited offers or at fidelity programs made available on the companies' websites.
If you don't feel like spending many hours in a train, you can consider travelling by plane. Especially if you have the possibility to book in advance, flying to Delhi can be definitely cheap.
Which stations serve the rail line Surat - Delhi?
The trains to Delhi will leave from Surat(ST) and will arrive at Hazrat Nizamuddin(NZM), Delhi Cantt(DEC) or New Delhi(NDLS).
When are the first and last trains from Surat to Delhi scheduled?
While the first train to Delhi leaves at 01:04, the last one is scheduled for 22:04. The average duration of the journey is of 19 hours, but the fastest trains can get you to Delhi in 15 hours and 47 minutes.