Doing XQs and tacos alone should be around 6m ish if you do it with all 3 chars a week. If you need more income, you have dailies which can average at 200k a day per char. I forgot the number of quest Freezer at franca cafe gives, but it should be enough for another 2m weekly if you do it with all 3 chars. Doing all these for a month should give you around 45-50m with minimal RNG influence.

If thats not enough to cover your needs, you can still farm stuff like alter/flicts, modulators, stuff for factors(latale demon soul, Vega soul and crap) or even rings. Bossing EQ for cubes, and seasonals for emper embraces will further your meseta income. While these are all RNG reliant, you will be more likely to get a 14* drop, than not getting gain from these.