With the addition of the 7Zee rewards club, this achievement has actually become about 100x less hard than it was previously before it. At 7Zee rank 22, the player is awarded a gadget called the Golden Sureshot. What this gadget does, is when hitting a gold slime with a fruit or veggie, you are garunteed that the gold slime will drop 3 gold plorts.
In order to reach 7Zee rank 22, the player must rack up a cumulative of 456,500 Newbucks, which is quite a lot. I will briefly share with you the method I used to get newbucks relatively quickly.
For this method you will need 2 fully upgraded gardens, 2 fully upgraded corrals and 2 fully upgraded silos. Put these 6 buildings close to each other because you will need to use them often.
I had a 2-way teleporter going from the lab to the docks. So I had 2 gardens at the lab and then the 2 corrals and the 2 silos at the docks. I put 25 mosaic slimes into each of the 2 corrals, totaling 50 mosaic slimes. I would plant 2 gardens worth of Silver Parsnips and then go to sleep. When I woke up, I would collect the parsnips, shoot them into the corral and then go right back to the ranch house and sleep again. Once there is 100 Mosaic plorts in the auto collector, you suck the plorts out and then put them in the silo.
(Note that since this solution was made silos have changed from having a maximum of 4 slots, to a maximum of 12 slots each. This means that we can store many more plorts and sell them whenever you feel the price is high enough.)
The goal is to fill each of the 12 silo slots with 100 Mosaic Plorts (totaling 1200 Mosaic plorts). You would also make the corrals hold 100 each after the silo is filled. (Equaling an extra 200 plorts). Then you would sell all 1400 of the plorts on the same day. If the Mosaic plort wasn't quite at the price I wanted it to be, (which was around 100-110 Newbucks per plort) then I would just sleep until it went to my desired price. Selling 1400 Mosaic Plorts for a minimum of 100 Newbucks each nets exactly 140,000 Newbucks.
Once you get to a high enough 7Zee reward level to get the vac upgrade that allows you to hold 100 of any item in your vac, it halved the amount of time it took to complete the process.
Once you have the Golden Sureshot, you must simply hit a gold slime with any fruit or veggie (sometimes hitting it with something other than a fruit or veggie, results in only 1 gold plort being dropped). Below is a video of my recommended farming spot for finding Gold Slimes. It is in the Indigo Quarry past the first Rock Gordo, the pond with the puddle slimes and across the bridge.
Alternatively, if you have beaten the adventure mode by reading all of Casey's emails, you can go to the teleporter Hobson opened up to his vault in The Moss Blanket. The teleporter to the vault is located past the Feral Hunter Slimes. You will need an extra slime key to access the vault however. There are tons of gold slime that spawn there and you are bound to hit one. Make sure to bring a lot of food to spray at the slimes. Be warned though, the gold slimes only spawn the first time you trigger them. They will not spawn on subsequent visits to the vault.
http://xboxdvr.com/gamer/Ace%20Annihilates/video/34750963