The easiest and fastest way to make money on No Man's Sky.
How to Make Money
Unlock Medium Refiner
First of all you need a medium refiner. But you have to unlock it. You need to go to space anomaly to unlock medium refiner.But firstly you need 10 salvaged data.You can find Salvaged Data by uncovering the Buried Technology, which is hidden underground on the planets you visit. To find some Buried Technology, turn on your Analysis Visor(press and hold F) and scan your surroundings. The icon you're looking for is a downwards pointing arrow, with a wi-fi like symbol on it.
After collecting 10 salvaged data you have to go to space anomaly. When in space, press x then select space anomaly.Enter space anomaly. Then go to construction research station. You can find it at the back of Space anomaly. In construction research station you need to find technology modules page.Then click medium refiner anf unlock it.
Oxygen & Chlorine
After unlocking Medium refiner, it's time to buy oxygen and chlorine. Go to any space station. Buy all of the chlorine and oxygen from the space station. Purchase oxygen and chlorine from visitors to the space station. If you are asking if we can collect instead of buying. Collecting takes much longer (especially collecting chlorine). It becomes much easier and faster to purchase.
Note: Chlorine is not sold in every space station. You may need to go to other space stations for this.
Chlorine Farm and Sale
Let's assume you bought 2K oxygen and 1K chlorine. To make a medium refiner you need 100 magnestic ferite and 5 Di-hydohen jelly. Magnestic ferite can be refined using a Refiner. Ferite dust -> pure ferite and then 2 pure ferite -> magnestic ferite.You can create Di-hydrojen jelly with di hydrojen or just buy from space station.Place the medium refiner on your base. Put oxygen up and chlorine down. You will need much more oxygen.
Start the machine and wait for it to finish. Take some of the chlorine and go to sell it. 4K chlorine will be ready, if you sell 2K of them you will get 1,2M money. For now, with the money you earn, buy oxygen from the space station and visitors there. Get the all oxygen you can find. Let's say you find 30K oxygen. Place 3 medium refiners on your base. You can put max 9999 oxygen in each. It gets faster with 3. You can get about 12K chlorine in about 2-3 minutes (you can get max 4098 chlorine each refiner). With 2 oxygen and 1 chlorine, you get 6 chlorine.
Put some of your chlorine back in the refiner and sell the rest.9999 chlorine costs about 6M.
It's that easy to earn millions in minutes. Do not forget to buy all the oxygen at every trip to the space station. You don't need to buy chlorine anymore.