Note: You won't be able to get this achievement the first playthrough and probably not the second. Prepare ahead of time by levelling WuJie and unlocking at least up to the 9th dungeon. As Long as you pay the rent every week, you'll be able to loop and carry over this progress.
This requires you getting the best score out of the remaining students at the end of the 60 day time limit. (I say remaining because they can randomly go broke sometimes, advantageous to us! >:3) The score is directly affected by only two things: How many objective stars you have, and your total gold at the time limit.
Specifically, every 10,000 gold up to a limit of 500,000 is worth +1 point and every Star is worth +5 points for a grand total of a score out of 100. I've seen the other students reaching scores from 65 to 90 so you want to really aim for 90 or higher to win. Getting the gold shouldn't be as difficult as fulfilling all ten Star objectives, though with enough stuff unlocked the only tricky ones are selling x items. The objectives are listed below, in order:
~Sell 50 items. (The count starts fresh every loop. Item quality isn't important.)
~Daily sales revenue of 5000. (Make 5000 gold from sales in a day.)
~Reach 100 Prestige. (Shoot stage plays once a week, treat everyone in the pub to drinks.)
~Gross sales revenue of 100,000. (Make 100,000 gold from sales in total.)
~Open the 4th dungeon. (Unlocked dungeons are kept between playthroughs.)
~Sell 500 items. (The most annoying one. I recommend using vendors with cheap gear.)
~Open all rack areas. (Buy them for 50,000 and then 100,000 in the Guild.)
~Daily sales revenue of 50,000. (Make 50,000 gold in a day. Sell Demon gear and it's easy.)
~Reach 800 Prestige. (Spend 30,000 at the pub on treats each evening for +70 prestige.)
~Reach the 9th dungeon. (Again, progress is kept between playthroughs. Probably optional.)
Keep in mind that unlocking dungeons will also unlock for purchase at the Guild any gear from the tier before, up to a limit of L80 Demon gear, so make that a priority. You'll make money far faster each day when you can buy or loot high level gear to sell in your shop. Lastly remember that you can save basically at any time and on multiple save slots, so if you're missing a few Stars and are not sure if you can win or not just save and pass time to find out. If not, you can concentrate on unlocking dungeons, recipes and levelling WuJie instead to make the most of that time instead of wasting it.