1. Do the index

2. Like @Havyeet said

3. Dark sector on pluto, 1 round (5 waves) then extract

4. 1 round of arbitration

5. Sell mods or items (if you played long, you will wonder how many oberon blueprint there)

Gather squad for High Risk Index make sure they're alright with carrying you and do at least 2 rounds of it or 1 at a time, 2 rounds will give you 500,000 or do it 4 times separately you get 1 Million Creds. 👌🏻 give it a shot try it ^^

For me, the profit taker is also a good option. After beating her she drops 125,000 credits and double with a booster. I am on Xbox and right now the fracture event is active which provides 2x credit and resources while in orb Vallis. It usually takes me 10-15 minutes to finish so can get 500,000 credits in that time and keep repeating it.

I don't know if you are able to fight the profit taker or that if you are on Xbox but I think this is a solid way.

If you're still in single digit MR (Lest you are very confident and really know your way around modding and how to set up your damage and have a strategy/tactic for dying less and killing lots) , I probably wouldn't do Index, because yes, you can lose credits.

And if 30,000 credits sounds like a lot to you (and you say it's hard) , you probably haven't quite learned or done enough with the game yet to be confident doing index.

Playing the game would have you passively collect duplicate mods and parts which you can sell for a few thousand credits a pop.

Neptune Index

Do the dark sector excavation on Europa

Oberon was once our credit king, now lord Harrow shall reign supreme. Do void fissures, get flooded with his chassis, sell them for good. A good side quest to keep those blueprint costs at bay.

Profit-Taker drops 125k,

250k if you use Chroma 4th ability just before Profit-Taker drops,

500k if you did above with booster.