Leveling help.

TheDragonHermit

Currently I have at:
Level 50;
Arlinn Kord
Dovin Baan
Kiora, Master of the Depths
Sarkhan the Mad
Sorin, Grim Nemesis, and
Tezzeret the Schemer
Level 44;
The Original Gatewatch PWs
Level 38; (ones I bought recently to cover missing color combinations)
Ajani Unyielding
Saheeli Rai, and
Ob Nixilis, Reignited (cause he seemed fun)
And Nahiri, the Harbinger at 31.
Currently the runes are just trickling in for me, so I would like any advice I can get for which PWs I should level first  and to what level.

hawkyh1

I would level nahiri and saheeli rai to level 40.
maybe ob nixilis also.

HH