Chara World can be quite a confusing space, as there are plenty of options to choose from in the bonus room. That being said, some of the previously mentioned options are not good fits, since they can be gotten elsewhere or are not top priorities. One such thing is the Critical Rate option, as you can always have it at 100% with the Curry Shop. Another option that is not important include the Weapon Mastery, since once you max it at 100, you have no need for improving the rank.
Low priorities include Movement, which can be remedied with Shoes until you start building up your endgame equipment (Carnage Trapezohedrons). Jump is also included in this, as well as Counters. Throw is not really important for anyone except for dedicated characters assigned for throwing (should be Wrestlers). Transfer Evility and Skill Secret Scroll are only really needed for whenever you need to create a scroll for either of the two, so they are situational.
That leaves the Equipment Aptitude, Learn Evility and Evility Slot NPCs as the most important of all of the options available to you. Aptitude is a good thing to have, with it maxing out at 300% for all of the stats. Learn Evility should always be the first NPC you check whenever you go to the bonus room, as there might be an Evility there that might be useful. The Evility Slot NPC is only useful for the first five times you talk to it, since you can’t get more common slots from it.
Maxing Equipment Aptitudes
One of the main uses of the Chara World is to max out a character’s Equipment Aptitudes, which goes all the way up to 300%. No matter how you look at things, it will be a bit of a grind to get the aptitudes to 300%, as usually the highest available is 150% or so. The first thing you will want to do, though, is reincarnate the character five times, as each reincarnation will grant an additional 5% to all aptitudes (up to a maximum of 25%), cutting down on a lot of grinding.
For the rest, you will want to concentrate on the Super Overlord difficulty, due to Miss Evil being exclusive to it. Once you encounter her for the first time, a new bill (Challenge an Evil Person!) will appear in the Dark Assembly, forcing Miss Evil to always spawn on the next CW visit. The reasoning behind this is that Miss Evil drops the Dowsing Rod item, which when used will always give you 2% for all aptitudes during that Chara World run.
The catch with aptitudes during any Chara World run is that they max out at 5% (the choice in the bonus room is separate from this), so getting any more than that is useless. There will always be a Dark Heart present at the beginning of every run, so that adds up to 3% that you can always get on every run. If you try for the other 2%, then it will entirely random. Getting the Imp/Orc event on a green mystery panel may have a chance to spawn two more Dark Hearts. Otherwise, you need to hope for a Hot Spring event or getting random increases from aptitude panels.