This was my first solo circuit. Taking responsibility for my own actions, here is what I did wrong: early downwind call to ATC was given and response was that I was #3 for landing and did I have #2 in sight. Scanning the circuit I saw an aircraft turning final. I responded that i did (my error) what I didn't see was the twin above me in the circuit. And I should have called I only have one in sight, what is the position of the other. My sense is that ATC also had the opportunity when both aircraft were on final to have called this. The low wing Dutchess and high wing C172 didn't help either PIC. My lesson: if you don't have circuit traffic in sight? Ask until you are clear. Thereby taking responsibility for your own separation. Don't rely on others. This 'luck to experience' transaction has made me 1000 times more situationally aware