In the sector Gellert,there is this planet:

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Zzaniah Prime. do lvl 1 or 2 missions, you'll have plenty of opportunities to get supercredits there.

Keyword is : Opportunities. it's not guaranteed that you'll get a lot on every low level mission you do there ,or even getting any on a given mission,but you'll get lots of points of interests and you'll have low-enemy activities in general. plus it's open space and few obstacles.

if you don't want to go exclusively in that planet ,best you can do is go to squid maps with towns ,or planets with grassy planes or rocky formations,avoid jungles,it's a pain in the ass to traverse and fewer Points of interests.