This will be the most time consuming of the Career achievements but isnt very difficult. You can skip the majority of the tournaments in a season once you reach and unlock the #1 ranking achievement. Then you will simply need to win enough tournaments to stay within the top 100 in the rankings. It is recommended that you play the majors in the season and a couple of the 4 star tournaments to maintain a decent ranking. You may not even need to play that many but you can easily check your rank after each week and if you see yourself getting close to loosing a top 100 position, simply win some tournaments to get back into position to qualify for the following years Masters.