Why is not enough?
It should be more than enough to settle in a system with a good neighborhood and get allied with the locals and stack supply delivery missions
You dont want to do wing missions that have you ferry like 5000 tons of something.
You want to stack many missions that want you to deliver or to source upto 180t of cargo (most of them should be in the tens of tons range - the 180t mission used to be called a Python mission

)
Pick as many of those missions as you can and do them stacked - delivery and Supply missions. Like get 5 delivery and 1-2 supply missions - and make sure at least one of the delivery is to a station you can use for the supply mission (or the other way around: more supply missions and some delivery - so you dont run empty to get those supplies)
Easy to get tens of millions per hour - but you need to be allied with all the factions in your home system - then to work on your trading rank (if you are low rank the missions wont pay as much)
And avoid Combat at all costs - it's not productive towards trading
For example,
this Python has 272t of cargo - it has minimal shields and minimal engineering (g3 drives, fsd and shields, g1 shield boosters and power plant) - no weapons.
Just win interdictions and if you submit dont fight - just pop a heatsink and boost away - it has enough speed to get you away from most combat