The first article I ever did for FR was about this very question!
www.foundationsrevealed.com/articles/fre...g-by-jenni-hampshire
My preferences remain pretty much the same now, but you will find that each corsetmaker does things differently depending on the effect they want to create and amount of time/effort they want to put in.
If you're making a contemporary hourglass corset, then I would certainly suggest trying a combination of spiral and flat steel to begin with. It is sturdy and reliable. If you're doing corsets with flat fronts, perfectly straight boning channels, or historically-inspired stays, then synthetic whalebone used en mass is a brilliant option.
Have fun