Depends on the starter, position, all that stuff.
Typically though, Belial first. I personally only really use the 5D(1) > DS launcher midscreen. A lot of confirms I found it's better to BE first so you can do the DS > 3C link for an easy 22C (especially if the starters have bad P1). But since I don't mind doing the cross under 22C, I usually do whatever. Whatever my hands happen to put out first, seriously pff.
Practically, yeah, Belial first, Deadspike as late as you can. Just do whatever man, Ragna is full of options kinda.
What's important is you make something out of every hit, doesn't matter what, and that you get usable oki~