@OP

Daily Stuff to keep the cash flowing:

1. Roulettes as adventurer in need
2. Retainer ventures --> sell what they bring back (can hit it big on this). The jet black dye alone sells for 600k on my server. Some other items such as the crafted primal weapons sell for a boatload as well

Other ways to make gil.

1. Clear demi materia III, which is easily obtained in Eureka, sells for 5k to a VENDOR (people are stupid enough to MB this, so dont). The Grade II sells for 1k, and grade I sells for 200g. Can EASILY make 500k/week doing this.

2. Materia farming, as you said. On a tuesday, throw up a PF for Factal Continuum speed runs to cap mendacity. Just MB any tier 6 materia u get. On my server the Vs dont sell high anymore. So I vender them also

3. Seph sap from Sephirot EX. Currently 4m on Famfrit