There's a fast way to get this achievement.
If you have 5-10k diamonds (less works as well, just won't be as fast), spend them all, then recycle your whole farm*. When you recycle your whole farm you get 100% of your money, diamonds and medals back. This then counts towards the achievement. If necessary, repeat these steps until the achievement pops.
*Make sure to harvast everything first and turn your resources in, because you will have a storage limit of 20/20 again, so you might lose a lot of resources.
Note: This works for the 500 medals achievement as well.