All the gorepacks can be purchased in the shop and you can avoid grinding coins by purchasing the gorepack you want then going offline. I did this with unplugging Ethernet, but I suppose disconnecting wifi should work the same. Once offline delete your local save file and then go back online and launching the game - rinse and repeat. You will require a minimum of 2,500 coins before starting this method.
Step 1. Go to shop
Step 2. Press A on the Gorepack you want, then A again to purchase
Step 3. Wait on the purchased splash screen for the achievement to pop (DO NOT QUIT/CLOSE THE GAME)
Step 4. Go Offline – Pull Ethernet, or Use Settings to disconnect WiFi
Step 4. Press Guide button, Manage Game - Delete Save data
Step 5. Go Online
Step 6. Launch the game - Go back to Step 1
Rinse and repeat for each Gorepack.
Enjoy your free time.