A few things I'd like to state:
1. If you get the carrot from the talking horse's caretaker, and then equip that carrot for fighting Rabi the rabbit succubus in the southeast forest/lake area, she'll chew it at the beginning of the fight and make it a far better weapon.
2. The best end game farming method for making money and levels I know is leveling the mushroom girl to 300, the mouse girl to 200, and Ilya the blonde healer to at least 100. Then walk into the forest to the northeast and use the advanced grimoire or Necronomicon and the best defense gear you have to take out all the shadow monsters first. Use a bunch of 30% strength restores at 22 health or below. Then clean up the 3 succubus on the map, careful to prepare before each fight, and if you've done that, you're ready. Now comes the money. After equipping your highest balanced stat gear and Chure's necklace, just walk over to the area boss and start the fight. Use the defense ability right away and just keep using it for as long as you want to make dough, your high level and passive 2% HP gain as well as Ilya's healing should keep you alive. Chure, the mouse succubus will meanwhile keep stealing money over and over, and if you bought the magic coin from the trinket merchant at the dock next to the sewers, she has 1/4 chance to double the amount she steals. You should also grab Chure's necklace from the crack in the wall behind the dock trinket merchant stall with Chure in the party while you're there. It gives chances to reduce the cooldown of her stealing ability further. Thanks to the levels gained and cheers from the mushroom girl, this method is by far more secure and much faster. Just watch a video and while spamming defense for an hour and by the end you'll have reached like 250K. You could boost the amount you make by going to stronger bosses that would give more money, but I don't know any that won't level drain of use a dangerous move at the start of the fight that's any stronger. You should also consider getting the blacksmith to make the true Aegis and Excalibur for you. I started by just fighting Chure and slowly grinding my way up btw. For some extra cash equip Catsuki's underwar while collecting items, but beware the loss of defense.--------- Once you get strong enough replace using defense with using the haste skill and recovering the HP with items or passive healing.
3. Make sure to use every succubus when interacting with right about every npc, to be thorough, you'll get high stat items with special effects that way. I don't know if every possible combination of party might have individual events attached to them, but at least some have unique dialogue. Both a blessing of immersion and a curse of grind. Also, interact with every object and odd location, like an alleyway that leads nowhere or a crack in the wall. You'll get items and hints for special succubus interactions for a select few.
4. I really wish there was a guide or at least a list of card achievements so I could feel like I got everything and did everything with certainty.
5. I'm not sure but it should be safe to assume that if you just want all the scenes, you can walk into the gallery and activate the cheat that unlocks everything. So, I guess don't worry too much about getting everything. More importantly, any enemy you've defeated will have all 10 variants of loss scene available so definitely don't set saves and redo fights over and over for every possible interaction.