What information do you think a first aider should gain about patient?

If you mean a first aider as in someone certified in 1st aid, assess the current situation (if I step in to administer 1st aid, am I putting myself in danger, creating 2 in need). Assess the victim. Is the victim conscious. If not, follow CPR guidelines. If they are conscious, ask them, or secondly a witness, what happened. Determine victims needs such as are they going into shock, having heat stroke, bleeding out, etc...