In order the get a better status, you must play EASHL or OTP games and get a certain number of wins, games played, and a certain overall grade. Getting the A- overall is not hard. Just play your position and don't cherry pick and you should be able to get an A+ in Position every game. Playing against human goalies makes is easier to get 2 points per game and get an A+ in stats. Team play is the hardest to keep up, but if you make some good hits, good passes, and don't turn the puck over too much then it should be easy to keep between B- and A-. If you are having a hard time, try playing D. It is much easier to get team play and you only need 1 point to get an A in stats.
Rookie 1 requires 10 games played, 4 wins, C- overall.
Pro 1 requires 25 games played, 10 wins, B+ overall.
Legend 1 requires 150 games played, 75 wins, A- overall.
If you are looking to boost this achievement, its very simple and surprisingly fast. You will need at least 4 people but more won't hurt. Go to Xbox Live > Community > Lobby and have one person create a room (press Y) and make sure to give it a password. Now everyone else can join that room and you won't have to worry about randoms. 1 person is going to play goalie on the losing team, and everyone else will play on the other team. Have one person score a goal and then quit as long as it's after the 18:59 mark. Now just rotate who is playing goalie on the losing team every game and you should be able to knock 100 games in about 5 hours.