I suggest mixing it up a bit.
Farm mission 6 on overlords for money(8.3k per run) and some items(around 7/10 mix boxes, 1/100 fortune box, close to 1/1000 of landing a legendary).
And mix it up with Ramboy, for items (6-8/10 mix box, 1/30-40 fortune box, 1/300-500 for a legendary). But it is a cheap energy mission that provides fussion materials,in colaboration with the other one it will provide u with a constat flow of fussion ans cash for fussion. Takes about 5-8 days for maxing out a myth, with 3 full 50 energy runs/day