- Farm relics and then open them i recommend you to do radshares. Radshares is 4 people with the same relic upgrading to rad. Get the whole set of the prime item (or parts) and list that item on warframe.market.
- Do sorties every day.And open or sell rivens you get from sorties.If you lucky you can hit jackpot like getting riven on rubico.But if you dont want to open the veiled riven sell it on warframe.market. For selling rivens easier use this site riven.market.
- Farm kuva liches.Depends on the weapon.
- Farm rare mods/Sell. Like primed mods or rare golden mods on warframe.market.
- Sell kavats or kubrow imprints.Sometimes you can get golden kavat that sells for a lot.
- Sell syndicate stuffs. Like guns, augments and more.
- Sell arcanes.
That is about it let me know if i am missing something in the comments.Thanks