You have several options to increase your AC.
Shield will increase your AC by 5 for a round and it's a life saver if you suddenly get swarmed. Though if you are not careful it can quickly eat through your few spell slots.
Honorable to mention blur and mirror image. Although neither increases your AC they both make you much harder to hit. Mirror image doesn't even require concentration.
Mountain Dwarfs have medium armor (but not shield) proficiency through Dwarven Armor Training trait.
Tortles from TTP have AC equal to 17 through their Natural Armor trait. That just speaks for itself.
Loxodons from GGR have AC equal to 12+Con through their Natural Armor trait. At first glance this seems less than 13+Dex, but being able to scale both your AC and HP simultaneously with Con, while disregarding Dex can make you quite tanky.
Simic Hybrids from GGR can gain a +1 bonus to AC while not wearing heavy armor at level 5 through their Natural Enhancement trait.
Warforgeds from WGE have the Integrated Protection trait, which offers a variety of AC options, some of which require proficiency in armor: unarmored 11+Dex+ProfBonus, medium 13+Dex(max 2)+ProfBonus, heavy 16+ProfBonus (and disadvantage to stealth). This trait is very powerful, but it won't edge out other options until the proficiency bonus becomes a +3.
Armor and shield
If you want heavy armor and shield, you will have to multiclass, the typical choices being a dip into either Fighter (which also gives you the Defense Fighting Style) or Clerics of certain domains.
For medium armor and shield you have a greater variety of choices.
On one hand, you could multiclass, the typical choices being again a dip into Fighter or Cleric.
On the other hand, you could get the Moderately Armored feat at level 4. However, to take that feat you need to have proficiency in light armor, which you could acquire from your race: Variant Human to start with the Lightly Armored feat, Hobgoblin for their Martial Training trait, and Mountain Dwarf for their Dwarven Armor Training trait.
What to choose
Each of these options come with costs, so which you choose depends on what you want to prioritize:
- Sorcerers have few spells known, so you may not want to learn too many defensive spells, but I really recommend taking shield regardless of any other choice you make.
- None of the playable races I have mentioned will boost your charisma, with the exception of an optional +1 from Variant Human, Simic Hybrid, or Envoy Warforged.
- Taking the Medium Armor feat will leave you relatively vulnerable at level 3 and will replace your Charisma increase at level 4. Moreover, although I personally prefer the Medium Armor feat I do not think it is a good option for you because it works best if the Dex is 13, which is impossible in your case.
- Dipping into a fighter will delay all your sorcerer features, while dipping into Cleric will delay all your sorcerer features except for the number of spell slots.
In your case, because your stats are all very high and you don't have to worry about being MAD, I think that dipping Cleric with a domain that grants heavy armor is the most effective option. You could do just fine with any race, but to maximise further I would pick the Envoy Warforged whose Integrated Protection beats out starting armor, and even surpasses plate armor at level 5.
In this case, your AC would be 16+[proficiency]+[shield]+[optional shield] = 20 to 25 AC at level 3.