You should be able to do everything for the Relic quest just fine. For Titan you will probably want to farm AK for the Level 60 drops there which has the side effect of giving you stones so you can get some darklight pieces.

AK is do-able in AF and regular level 50 weapons, Ifrit and Garuda are both do-able with GC or Level 55 crafted weapons. You will probably want an Ifrit or Garuda weapon for Titan though.

Keep in mind that you will want to gear up your BLM for the relic quest just as you need to gear up PLD. Titan will murder you if you don't have AK gear or better, you will need the VIT increases from it even on BLM as you will have to live through unavoidable damage. So there is no rushing it, you will have to get geared up.

I would recommend doing AK over CM runs anyway until you do get the Level 60 gear drops from it. It also gives you mythology stones which you can save for Relic +1 or the Relic armor.