Hello Annapurna !!Documents required for GCET application form are:

1.3 passport size photographs that should be taken 3months before filling the form.

2.copy of SSC passing certificate

3.copy of +12 passing certificate

4.DD for the application fee.

https://engineering.careers360.com/articles/gcet-application-form

You just go through the above link, you can get more information about gcet.Hope i might have helped you.Good Luck!!