if you utilize the map well, you'll never run out of berries.

just blip the map any time you come across a group of berries when you explore.

my map is FULL of dots labled;

• 4 raspberries
  
• 5 blueberries
  
• 3 mushrooms
  
  if you got the fenris set you can just speedrun around to shorten your berry run. berries respawn (that have been picked, destroyed bushes don't) eventually so i don't even go to everything i've labled. just run through a nearby spot every once and a while.