Plains of eidolon is good, but way too heavy on the grind
An ostronsigil would be nice or smaller standing rewards for taking out eidolons, grineer camps, discovering the map or simply trading with them. The quills is the same. Standing gain is sluggish at best, dropping an eidolon and managing to get all exceptional and intact cores nets you a 1,5k standing at best, that's a horrible rate.