The further you go ingame, the better your weapon, the more you'll regen your focus.
The standard combo when your cold snap is in CD is RMB -> LMB -> 2, rince and repeat. depending your badges, you may want to replace 2 with a frost F.
Don't forget that Dual Dragon has no animation cooldown, thus can be put between LMB and 2.
My frost combo used to be (cause now I'll have to re-learn from scratch with that awaken mech) :
LMB -> RMB -> 4 -> Z -> LMB -> RMB -> X -> X -> 2 (Keep 2 pressed until cold snap fades out) -> LMB -> RMB -> 2 (repeat that part until Cold snap is out of CD).
WIth fire orb disabled, I won't use F with that fire orb. Though, I'll have that frost orb used to have that extra frost damage. So, replace any 4/Z/X/2 for a Frost orb (F) and put that dual dragon (F) whenever you can.
With that, I never had any trouble with focus, and maintained a steady DPS (With Raven 9, purple badges and only BT accessories, BT 3/8 / VT 5/8 SS , 180k DPS approx. Now, with Raven 9, same SS and leg fire badges, i'm around 230k DPS. Both without either BB or SB)
Keep note that with today's update, things are gonna change. DPS-wise, but also rotation-wise