If you dont have the confirmed ticket on this train and you are planning to travel in general boogi then first check for the weekly trains leaving from ADI (Ahmedabad) towards Mumbai around that time so you can easily find seat in GEN in that trains and you will not have to stand in queue reaching station before 2 hours of departure of karnavati express.
That will faint you and also standees will totally embarass you throughout the journey. Else you travel in other weekly travel GEN boogi.