It takes no more than a month to take your team into CC levels from what I remember. And frankly, leveling 30-50 costs pittance compared to trying to raise CC56+ units higher, so don't worry much.)
And until you have G-tier Gold daily on farm, Platinum Armors are a bit too rare to use them on your level 30 units. Bridging 40-50, sure, getting your healers / archers / mages Class Evolved help a lot on low levels (just don't forget to serve them with three spirits of rarity matching to unit you are trying to raise).
Frankly, you have quite a lineup. Gold archer that is arguably on par with platinums, best gold mage, a freakin Princess and very durable one at that and one beast of a woman with most likely highest dps platinum units can hope to achieve (versus soft targets).
And Sophie, who is simply a monster, even on low levels. Seriously, you can just drop her ahead of your most troublesome foe(s) and pop her skill seconds after to turn her into a unholy rape machine to grind them to dust. Granted, she really blooms with skill levels (as she is dependent on it to be active), Class Evolution and, as everybody, affection, but still, she is quite a catch. And her disengage when skill ends can actually save her behind should you let her take on too much enemies and leave her too banged up) And even in inactive state, she is excellent lightning rod to make ranged enemies waste their attacks on, saving your squishier units from the fire (If you weren't aware before, ranged enemies target last placed unit in their range (unless tanked, then to tank their attention goes), so you can place your lightning rod last and they all will focus their fire on her ignoring your other units.) Team-wide regen is a cherry on the top.
For now, get Katie and Cloris (it is important, especially Katie, she's the best soldier you can get for free now and is quite a defensible), bring your team up to ~25 (Pastoral Gate works) and take Return to Ruins to Commission Sortie. You will do most of your to-50 leveling here, until you reach Fiery Oasis and then Base Scramble II. Actually, make reaching these two maps your priority, beelining to Oasis as soon as Desert maps are unlocked, evens 1* skipping Castle Retake and everything in-between and ignoring last Kingdom maps for awhile.
And if you are really desperate, you may buy a full set of Shrine Blessings and power through maps to the best grinding spots (but I would recommend to raise your army normal way more first).
Novice One appears to have a reasonable low-level play-through on a cursory glance. "A non-billing Prince's Aigis" also does an extreme low level playthrough... Maybe that channels will help you, as Eth Eternal did) .