credt to Devious Jedi
I have found the easiest way and its the way i got this achievement so i know it works is to complete the game as you normally would, now chances are if you havnt been replaying certain levels over and over to get this achievement then you will not have by the time you complet everything else.
Go to gringotts and complete the 1st room, no go to the level builder and place 10 devil snare plants and 10 purple coins. go to test or play level.
Kill the devil snare and collect the 10 coins and finish level and replay untill the achieve pops. i only had to do this twice before i got it.
*edit - apparently you do not need to finish the level to get them to count. view comments for more details.
*edit - apparently you do not need to collect studs to have the points count. Just kill the plants!
worked for me on the second try. could only place 8 tho. turn on stud magnet and multipliers to make it super fast.