Minimum sizing. If you can "size" them in a Lee FCD (remove the crimping parts) and the cases fit your cylinders, that is all the sizing you should do.
Seating: Yes, you want a "flat" seating stem, but, depending on the bullet, you might want a relief hole in the center so you don't flatten the "button" nose.
Exapnsion: Better to over due than try to go minimal. You will want to seat about ¼" of bullet in the case by hand and verify that it is as straight as possible. Pushing down on a bullet from the very top, and having a very long bullet to push down, means the bullet will want to tip very easily.
Crimp: you either seat the bullet just under flush and give the case mouth a very slight roll crimp or you crimp into a crimp groove. Best crimp die is the Redding Profile Crimp die.
Both the most accurate bullet and the least expensive bullet I have found is the Remington L-HBWC. Do not load over 800fps. If you load a DEWC or other non-hollow-base bullet, you can load hotter.
