I just recently learned this after 110 hours and I wanted to share it with the people who struggle with scraping up Nanites. In no time, you can produce as many Nanites as you can process. – find yourself a nice world, mild weather, friendly creatures, passive sentinels. I found a very nice paradise planet in Eissentam. – land and start walking in one direction. Keep checking your surroundings with your scanner. At some point you will find your first curious deposit (Runaway Mold). Jackpot. Set up a base. – secure the deposit: usually they grow on hillsides so you want to use some wood prefabs to build a funnel for easier harvesting. Find maybe one more deposit and repeat, you don't need more.

The best part is: the Runaway Mold respawns IMMEDIATELY after you left the immediate area. That means you can travel back and forth between two deposits and keep harvesting continuously. Set up as many medium refiners as you can (medium refiners are perfect since they don't need power/fuel) and start printing Nanites! Enjoy!