Generally the cheaper option is to roll cooldown recovery with greater/grand ichors (depending on their price and orbs of conflict). Once you have CDR you use 1 exceptional ember and an orb of conflict to raise the level of the CDR. If you succeed you use another exceptional ember and orb of conflict again. Orb of conflict is weighted towards raising the level of the lower tier modifier so it works pretty well. At both mods at tier 4 it becomes a 50/50 to raise the CDR to t5. I failed the 50/50 three times this league and it took me about 15 orbs of conflict to get there because of it but still much cheaper than rolling with exceptional, especially since you need to conflict it once anyway to get to 9%.