This is after you finish main story line.

1. Start your relic quest.
2. Grind CM/PRAE and upgrade your gears.
3. Do Wanderer's Palace for better weapons/gears.
4. After getting better gears, you can start Chimaera.
5. Repeat 2 - 3. Then do the relic quest up to Hydra or so.
6. Farm AK for Philo/Myth for seals/gears.
7. You can probably do Ifrit HM easily now, maybe farm it so you can get Ifrit weapon.
8. Farm AK/CM/Prae/WP for a bit.
9. Do Garuda HM.
10. Repeat step 8.
11. Do Titan HM with most of your Darklight and a strong weapon.
12. Farm AK for end of relic quest and upgrade your relic to +1.
13. Do Bahamut's Coil.

You can do this in any order if you please I suppose but just my 2gil.