This is a fairly simple achievement and can be earned in as little as 1 game (maybe 2).
From the top menu, select eFootball, then Online Divisions and you will be greeted with a graph showing that you are in Division 12. You need 300 points to gain promotion to Division 11 and thus pop the achievement.
to launch the next match and select your team. You'll notice that the lower quality of team you select, the more points you can earn from the game. Select your team and search for a match.
Upon completion of the match, if you won, you'll pop the First Online Divisions Win achievement if you haven't already. Then you'll be shown the graph again with your points total indicated. Note: if you have 300+ points you will not
automatically pop the achievement. You must press to end the season with the current standings
and you'll be promoted to Division 11 and thus will gain the achievement. If you don't have 300+ points, keep playing matches until you do, then end the season as soon as you meet the requirements.
Hope this helps. If you dislike the solution, please tell me why so I can improve my solutions going forward.