To unlock this achievement you simply need to gain 50 Battlemarks after having activated your Rank Chip at level 32. Each gametype will have a set rules, they can be checked from the main Lobby / Ranked Play / Game Mode Rules. Complete any of the scoring events listed to increase your Rank and Battlemarks. You will however lose Battlemarks for dying and staying offline to long as they will decay. Collect enough Battlemarks and the achievement will be yours.