## What is your party *facing* for foes?

That is the primary question that determines what your optimal spell choices for combat *actually are* -- different encounter types favor different spells.  (I am limiting myself to feasible encounters for a low-level party; clearly, an illithid or adult dragon is a whole another story...)

* Sentient humanoids in small quantities (whether it be a orc/goblinoid, cultist, bandit, or more exotic theme) -- these encounters play straight into your hands with *charm* and *suggestion*, especially if you can identify and target leadership figures within the NPC ranks, and doubly so if you are facing NPCs with poor mental (usually Wisdom) saving throws.
* Swarming humanoids (goblins, kobolds) -- again, identify and target leadership figures.  Being able to charm the goblin war chief into making an entire company o' goblins bow to your feet beats the pants off fireballing them and then having to spend several rounds mopping up.  Bonus points if you can convince the war chief and his company to fight alongside your party for a while!
* If you are dealing with a leader-less swarm of humanoids, you still can sow considerable confusion within the NPC ranks with well-played *charm* or *suggestion* spells.
* Swarming monsters (stirges, etal) -- this is bad news for you, and where AoE crowd control (one of the normal mage specialties) is most needed. Hopefully, your DM's Inspiration is a recognition that you're playing a character that fits well with his future plans, and not simply "this character is underpowered, so it *must* be good RP"
* Predatory animals (wolves, bears, etal) and monstrous predators (owlbear, anyone?) -- unfortunately, you are now in Druid territory; Sorcerer mind-affecting spells are designed to attack humanoid foes for the most part.  (*Sleep* is vastly underpowered in 5e as it works on a hit *point* basis.)  Thus, you're stuck with direct damage as your only remaining option...thank gosh for damage-dealing cantrips!
* Mindless undead -- this is the realm of turning Clerics, as most low-level undead don't have the brains to understand your *charm person* and *suggestion* attempts.  Again, you'll need your damage cantrips here.
* Fiends -- these are flatly, a pain in the rump, even if you are dealing with their weaker forms.  They have nasty damage resistances *and* magic resistance -- very few things can deal with them well (fey knight paladins get the *turn the faithless* class ability which helps, but that's about it).  So, I wouldn't worry about your effectiveness against them.

## *Shield* is more powerful than you think...

Their criticism of *shield* is off-base as well; it is actually one of the most powerful defensive spells available to an armor-less mage of any sort, because its +5 AC bonus stacks on top of *both* your DEX modifier and base AC from other sources (such as *mage armor*, your Draconic Ancestry, and *barkskin*) *and* is available as a *reaction* against someone attacking you.  In other words, you have 18+DEX AC available to you *whenever you are attacked*, despite wearing no armor whatsoever.

## Use your Inspiration well

Rerolls are very powerful to have in your back pocket, especially against a DM that imposes harsh penalties on failures, or against NPCs that are fielding save-or-suck effects.

## Be gentle on your DM

Mind-affecting spells such as *charm person* and *suggestion* are much more stressful on DMs than straight damage is -- the latter is mere book-keeping, while the former force them to adjudicate an inter-NPC conflict, and can even take them places that could otherwise break a campaign.  (The goblin war chief thought joining you was a good idea -- now the DM has to deal with bookkeeping *two* NPC parties, one of them hastily reinforced due to the incoming goblins, as well as your own!)

## Future spell suggestions
While your theme (ambush back-line leadership with charm spells to disrupt the order of battle) isn't at all bad (save for Spell Sniper not working with save-or-X spells), you may wish to augment it with more combat-useful charm effects and complementary spells.  My suggestions for this theme (going from second to sixth level spells) would be:

* *Crown of Madness* -- very useful for disrupting battle order, and at a good distance too
* *Detect Thoughts* -- get inside your enemy's head
* *Invisibility* & *Misty Step* -- you'll need some help skulking around to get in range for your save-or-X spells, so *take it*
* *Counterspell* -- *shield*'s counterpart for going up against higher level casters
* *Fear* -- AoE crowd control, mind-affecting-style
* *Gaseous Form* -- more sneaking assistance
* *Hypnotic Pattern* -- medium-range AoE charm/crowd-control
* *Greater Invisibility* -- cast your spells *while invisible*
* *Dominate Beast* -- be the bane of the dogs of war
* *Confusion* -- throw entire war parties into disarray
* *Dimension Door* -- your first outright teleportation ability
* *Dominate Person* -- obvious choice
* *Mass Suggestion* -- again, obvious