Farming in Noita means banking the two things you cannot make: gold and flasks.
What to bank
Gold buys wands and perks at shops. Flasks are healing you cannot recover. Both matter more than materials, which you find by playing anyway.
The calm biome trick
Clear a biome you can do without thinking. Take its chests. Leave. A biome survived twice gives more than a hard one you clear once on luck.
When to stop
Stop farming when your wand chains cleanly and your flasks are full. Past that, more gold buys little you can use. Push forward instead.
When not to farm
Do not farm a hard biome to top up. If you are already low, the next biome is the path; a risky farm that kills you spent the run for gold you cannot spend.
The biome guide shows where the safe farming sits in the world order.
Bank before you push
Farm gold and useful spells in the early Mines, where enemies are weak and loot is steady, then drop back into a holy mountain to lock in progress. Pushing deep while poor just trades a safe loop for a wipe that loses the run.