Welcome,
With 2k cost minimum of training flux lora quite a few users can actually do that regularly and training single character unless it's "top tier waifu" won't even pay for itself.
So i keep tying to make on-sitre traing for multi character loras work, with this article i want to share what i realized and invite You to share Your insight.
My first attempt was to make pack of Dungeon Meshi main crew, then i had completely no idea what i'm doing, now i'm just kinda have no idea what i'm doing.
The process was: default settings for flux lora training, captions, i changed nothing in training parameters.
It was completely failure, it got my unholy amalgamations of the group features, unable to generate any of them.
Then i watched Steams with KFTiger, and read Valstrix's Crash-Course Guide to LoRA (& LyCORIS) Training, after that i realized two things:
Not every Flux lora need captions, you can train character/style with tags, and keep captions for more advanced loras.
The most important change in training setting is to put train batch size at 1