I have pumped quite a bit of time into this now gonna drop some tips and observations.
To recruit male party leaders to Taron's party you have to get them to 100 affection then kill more of the map bosses than the party to invite them into Taron's party. To recruit female party leaders you have to get to 100 affection let the entire party die then finish the map by yourself to invite them back to your house to "heal" them, dragongirl seems to have some weird extra flag that the other girls don't so you might not get to invite her even though you have 100 affection.
You can give gifts to people to raise their affection but as soon as you go over 80 further gifts wont have any effect you got to get that last 20 affection through actually partying with them.
The value of loot that people drop when they die is directly tied to the parties average level so counter to what most people in the thread have been saying raising a parties level is beneficial you can buy items out the shop that can reduce the party leaders health by up to 90% at the start of the map so you don't have to worry about a female lead party becoming to strong for them to die off to capture them.
Letting the party die is not always the best option for making money typically speaking the sub level 10 parties will drop less loot than the reward for completing a Gale valley map and completing an underground cavern map is better than any parties loot except the Golden Lion's party. It is often better to use Taron to help with the fighting on the gale valley and underground cavern maps especially with the mid level parties as the reward for completing the map will be better than looting the dead and then bailing.
During Taron's spinning special attack he take no damage whatsoever this is very useful for clearing out a path through a large amount of mobs, finishing off boss monsters or getting through a bullet hell projectile spam. Taron is also completely invincible during rolls you can use this to your advantage because projectiles will still disappear when they hit him so you can roll through them to protect other party members from taking damage not too useful early on but towards the end of the game there are some brutal projectile spammers.
You should prioritize raising Taron's level over his equipment you can turtle your way through most of the early game without taking any damage and the better parties that require Taron to be at least a certain level before he can join are much stronger and allow you to collect resources, loot better items from dead and claim the reward for completing harder maps. That said his shoes are worth upgrading because the speed boost is a massive mobility increase making collecting items and shepherding/kiting enemies much easier.
I would say that it isn't worth Taron forming a party until you have at least 3 other party members, until you hit the harder maps you can only really bag a small amount of exp and the map resources early on because there is no reward and party members don't drop items when they die you can make money by hiring mercenaries and getting them to die but if they survive you end up spending money for nothing its not really worth the gamble to be honest as soon as regular mobs start dropping demon cores you can start making a bit of money by selling them they are the most plentiful resource by far if you don't sell them you will have more of them than anything else by far you can make a modest amount from the 50+ enemy maps not more than from completing a recruitment mission but at least you get all the exp.
I also recommend backing up your saves before initiating H scenes if you plan to play the game legit, the game can occasionally crash that by itself isn't a problem since the game autosaves regularly but it autosaves during H scenes and if the game happens to crash during a H scene when you reload you will have a persistant softlock as the H scene will crash again basically ruining that save file.