Just completed the Chaos route this morning. I should have turned the difficulty up because it ended up being far too easy after the initial bump at the start.
A few hings I learned that would be useful for others:
Agility based damage dealers are very likely your strongest option for most of part 3 due to auto-Sylph and how easy it is to get Technique Converter; Alice out-damaged the powered up Luka on the final boss. Alice, Zion, Alma Elma are high priority characters, but since a large portion of their damage comes from Vanguard/High Vanguard, you only want one of them on the frontline.
Lily of Compassion is probably the single strongest race for supports. I didn't use it enough until the final dungeon and that was a huge regret; it automatically deploys multiple major buffs on combat start, allowing you to focus on other things. The fastest available option for most players is going to be Adult Promestein; she also has good access to Medicine skills like Doping, but you can just as easily swap her out for a your choice of Dancer.
Triple Wielding is the strongest option at the start of the Chaos Route but falls off at the very end when you get access to strong accessories with multiple Gem slots.
If you aren't doing a Crisis build, the Sealed/Forbidden Land Dweller races have one of the cheapest possible stat buffs fairly early in their line.
You get enough Job XP to max out lower tier jobs very quickly. It takes around four or five fights for a character to max out Advanced Maid and get double Job XP - hunting down Sealed Proofs is more important than filling out Forbidden jobs you don't really want. Never waste job XP if you can help it.
On the topic of Proofs, there are much fewer caster Jobs than physical Jobs, and the Forbidden caster jobs come around the midpoint. The main advantage of Casters is that when you start quintupling your character's costs by stacking Over-Boosters, it feels good to use MP.
True Form Tamamo is very good but not a good as she sounds. Her stat doubling takes the form of a buff which does not appear stack with other stat buffs.
Magical Girl Granberia absolutely fucks, but her natural haste can work against you since she tends to accidentally step on the toes of Agility DPS's and act before support buffers
Illias does eventually get good but never gets as good as the other heavy hitters. Her most important duty is standing next to fused Eden during the final dungeon.
