I'm making a shirt for a (rather egotistical) friend of mine and so am trying to do something with the slogan "I am the best" for fun. I need something with four characters only, and would like to ask the difference between
私の一番, 私が一番, 私は一番,
and which one would be the most appropriate in the context that he is saying it of himself. My grammar is not fantastic. I understand that が would entail a meaning like "I am the number one" versus は which would be "I am a number one" (correct me if I'm wrong). One of my friends has suggested
俺が一番, 俺様一番
Can someone explain to me how 俺 and 私 differ then? I'm quite confused. Also, this is for a boy, just in case anyone wonders.