It's not time-consuming to unlock Oerba 400 or to spawn Zagnahl with some frequency (I do have the Encounter-rate fragment skill). But farming Power Essences is incredibly slow when you earn them one at a time, especially since you're likely to be using them three or five at a time. Not a great method.
In the Archsteppe, Moblins seem to spawn very rarely (I don't have the BattleMania skill - the one that makes rare monsters show up more). So farming them is time-consuming. Even though you get three power essences at a time, it appears to be slower overall than Zagnahl. Doing all of Professor Paradoxes maps is, of course, pretty time-consuming, so that's not much of a "fix." If there is a specific spot/weather pattern in ArchSteppe where you can spawn Moblins more regularly and without the fragment skill, let me know.
Chocolina sells Power Essences for 1,950 each. I have about 100k. So I could buy a lot of them, but I'll use most or all of my money on one thing. Is there is a gil-farming method that makes this way of getting Power Essences faster and more efficient than the two above?
I'm not 100% sure on how far you are in the game, but since you mentioned Oerba 400AF I assume you know about Raspatil. If so you can farm it repeatedly while having Durable Collector's Catalogs on Serah and Noel for some serious cash each time you fight it. That said, though, by the time you're strong enough to reliably farm it you should have Battlemania unlocked anyways, making farming the much easier Moblins a breeze.
I didn't actually know about that enemy, but Oerba 400AF is the most recent area I've unlocked.
There's nothing stopping me from getting the BattleMania skill other than my own lack of desire to unlock/revisit *every* area and get 100% of the map. Obviously I would do it if I were planning to 100% the game, but mostly I just want to get all eight paradox endings and defeat all of the boss-type monsters in the game. I have 5/8 endings and several bosses to go.
The reason I stopped to gather power essences is that Noel and Serah had gotten WAY more powerful than my COM, which was just a max-level Dragoon. I have a decently leveled/infused Cloudburst - same for Goblin Chieftain, but my COM has falled behind. So I built Chichu up to level 38. He has about 620 STR, but his HP still kind of sucks and it seems like he needs a good 7-8 more levels to become anything noteworthy.
Well, he has low HP at that level because you built him with power materials. He'll be a badass (well, a fully upgraded Chichu is badass no matter what you build him with) attack-wise for sure with those, but he'll be completely useless against enemies resistant to physical attacks, and have much lower HP than if you had built him with potent materials, like I did, and which I would recommend (potents are much easier to farm as well). I know most people here disagree with me though, so whatever.