If solo is your mindset then not going for Bozja is a mistake. You don't even need to actively participate in FATEs or Criticals, you can just go around farming mobs for Fragments, doing this actively and efficiently even solo is a great way to make gil. It's actually what I'm doing most of the time at the moment so I can progress relics.

There is also attempting solo Heaven on High and Palace of the Dead. It'll take you a while to reach the higher floors, and consistently, but when you get there, the Gil you can make from it is incredible.

Aside from that, just running dailies, and doing solo raids like Coils of Bahamut and then doing desynth'n loot from both is quite nice. Granted the former you generally do passively.