You were given good and quick advise on how to get started with GSoC on the Gitter channel. It is not too late to apply but don’t waste any time: the submissions close on April 19!
If you need more guidance or advises, reach out here (or on the Gitter channel).
Sidenote: the “GSoC mentor” group is reserved to mentors only (archives are public). This is why I am redirecting you to this channel/topic (and turned down your request to join to the Mentor’s group).
GSoC Org Admin