Easy way to grind for all manticore guns. (took me about 6-8 hours getting two guns from g3 to g5 while also trying to figure out most of these methods)
Weapon schematics: Take any larceny mission, go to the site, DO NOT TAKE THE ITEM REQUIRED FOR THE MISSION, relog to main menu and all will reset.
manufacturing instructions: Look for salvage mission for encrypted/normal memory chip from impact site. Check the data port, relog to main menu, repeat. DO NOT TAKE THE MISSION ITEM TO KEEP THE INSTANCE
Ionised gas: Find a system with lots of stations close by. (personally used sol). Under operations, look for on foot missions that need you to disable/impede production. The missions will give upon accepting an item, either some catalyst or ionised gas. Accept and then decline the missions only giving you ionised gas. WARNING: declining the missions will result in fines for the faction
Microelecterode: Again with the larceny missions with the weapon schematic. Go to the crashed SRV, cut open both panels, loot the items, log to main menu repeat. By having a mission you can relog to the same place every time. Trade the items at a bartender. (every instance is almost guaranteed to give/provide with enough materials to trade for 1 electrode. Also easy way to grind all circuits you will ever need.
Chem superbase: Get to Arai's Mine in Iah Bulu system. It's a high security settlement with very few guards present. Your route will be: disable alarms (there is a guy on the second floor on the CMD building that you can scan through the window) loot the small HAB next to CMD, loot the POW for ionised gas/schematics/other stuff. Then the big HAB building. You will be mostly looking for graphene/epoxy adhesive. These two trade for the highest rates in bartenders and are plenty there. To reset the instance just take off, engage fsd, drop immediately, fly back, loot, repeat.