Argon Crystal - These can be obtained through enemy drops in Void Missions - TIPS: For increased drop rate, use Resource Boosters, Warframe abilities such as Pilfering (from Hydroid or Khora) or Desecrate (from Nekros), break Argon Deposits, and play with a squad (more enemies, more loot)

Circuits - These can be obtained from drops on missions. The best missions for these are Cerna (Ceres), Seimeni (Ceres) and Venera (Venus) - TIPS: For increased drop rate, use Resource Boosters, Warframe abilities such as Pilfering (from Hydroid or Khora) or Desecrate (from Nekros) and stay longer in missions such as Survival

Fish Oil - Catch some fish using your fishing rod and then take it to a fisher merchant to convert them to oil. (e.g. Catch fish in a lake in Plains of Eidilon on Earth, and take them to Fisher Hai-Luk in Cetus) - TIPS: Best fish to catch are Twilight and Mortus Lung Fish (abundant during the day in Lakes), Norg (best caught at night in Ponds), Charc Eels (can be caught day or night in Rivers). For more visibility of the fish, use Luminious Dye (can be bought from Hai-Luk) and carry multiple Spears and bait types to handle different fish sizes and environments

Grokdrul - These can be found in Plains of Eidilon, on Earth, as cannisters in Grineer camps (marked by a little mountain icon on the map) - TIPS: Focus on breaking the glowing cannisters in Grineer camps, rather than relying on enemy drops. Nekros' warframe ability Desecrate can sometimes double drops from Grokdrul cannisters

Iradite - These can be found in Plains of Eidilon, on Earth, mainly around Grineer bases (marked by a little mountain icon on the map), they appear as black rocks with little red glowing rocks on them - TIPS: These can be found near cliffs, rocky areas and Grineer camps, look near Gara Toht Lake, Twin Horns, and Northwest of the Seethe for increased chances to find them. Use Mods such as Thief's Wit or Animal Instinct to highlight loot. Using Archwing will also help you find them easier, because you can search from above

Kubrow Eggs - These can be obtained through Earth Missions - E Prime (Exterminate), Eurasia (Mobile Defense) and Mantle (Capture), all you need to do is find Kubrow Dens and destroy them. The Eggs are not guarunteed to drop, so you may have to keep replaying the missions - TIPS: Use the Codex Scanner to find Dens easier and once you have destroyed some dens, leave the area to find and destroy some more and then go back to the previous area and the Dens will have respawned

Neurodes - These can be obtained through enemy drops, the best places to get them are Lua (Plato, Tycho), Eris (Oestrus, Zabala) and Earth (Everest, Tikal) - TIPS: For increased drop rate, use Resource Boosters, Warframe abilities such as Pilfering (from Hydroid or Khora) or Desecrate (from Nekros) and open Resource Crates