For training I use the onsite trainer. A lot of the settings stay default but I typically set it for Epochs 10 and 14 repeats to give it 2100 steps with 60 images, Clip skip 2 and Prodigy for the optimizer. But I think what really helps is finding as high res images as you can. For TV show characters I usually use google or bing image advanced search to look for high resolution images. Particularly ones from promo photo shoots if I can find them. Also if I can't find enough from the show I'll pull a few images from photo shoots or other shows the actor did in the same time period.

@beitris I've heard that but most of my flux celebrity models are trained on 60 images and they came out fine. That being said I have done ones with as few as 30 images and still was able get a decent results. I like to have about a 50/50 mix of closeup head shots and full body to wind up with a consistent face plus body/pose data.