Stay out of range
Many spells have ranges greater than 60 feet, and you'll likely have 30 feet of movement so you can get out of Counterspell range as long as the enemies are 35+ feet away. Then try some movement-lockdown spells to keep it that way!
Cast 4th+ level spells
Don't bother with 3rd level spells or below, they will definitely be Counterspelled. Go with 4th level or higher - Your average enemy caster who isn't an Abjuration Wizard or Lore Bard will only manage to counter your 4th+ level spells about 50% of the time or less.
Go invisible
An enemy has to see you to Counterspell you. This will prevent you from casting Concentration spells as you need to concentrate on your invisibility.
This could also be substituted for similar line-of-sight-denial tactics, like Darkness & Devil's Sight Warlocks.
Bonus action spells
You can cast spells with your bonus action (not more than 1 1st level spells in a turn though). Since two enemies can only counter 2 of your three available spell actions (action, bonus, reaction), you can use your bonus action spell to:
- Get a cantrip off - at least you're then doing something.
- Bait enemies to counter a cantrip and then unleash a big spell.
Baiting works because there are no rules that allow anyone to identify a spell being cast, other than the following one in Xanathar's:
Identifying A Spell
Sometimes a character wants to identify a spell that someone else is
casting or that was already cast. To do so, a character can use their
reaction to identify a spell as it's being cast, or they can use an
action on their turn to identify a spell by its effect after it is
cast.
If the character perceived the casting, the spell's effect, or both,
the character can make an Intelligence (Arcana) check with the
reaction or action. The DC equals 15 + the spell's level. If the spell
is cast as a class spell and the character is a member of that class,
the check is made with advantage. For example, if the spellcaster
casts a spell as a cleric, another cleric has advantage on the check
to identify the spell. Some spells aren't associated with any class
when they're cast, such as when a monster uses its Innate Spellcasting
trait.
This Intelligence (Arcana) check represents the fact that identifying
a spell requires a quick mind and familiarity with the theory and
practice of casting. This is true even for a character whose
spellcasting ability is Wisdom or Charaisma. Being able to cast spells
doesn't by itself make you adept at deducing exactly what others are
doing when they cast their spells
-Xanathar's Guide to Everything (pg 85)
Since this takes an action or reaction, it can't be paired with a Counterspell. So the enemy will not know which spell you're casting.
This only works vs. 2 enemies, 3 will be able to fully counter your action, bonus action, and reaction.
Action Surge (Fighter-multiclass-only)
The ability to take more than one action on your turn means you can cast more than one spell. Only increases the number of casters needed to shut you down by 1 though, and you almost certainly will only get 1 use of this in a fight (unless you're a 17th level Eldritch Knight, in which case the solution to this problem for you is "hit them with weapons instead").
Subtle Spell (Sorcerer-only)
When you cast a spell, you can spend 1 sorcery point to cast it without any somatic or verbal components.
You need to be able to see the target casting a spell to Counterspell. Subtle Spell will stop spells with only verbal and/or somatic components from being seen.
Contingency (Wizard-only)
When a spell is cast with Contingency, it cannot be seen to be cast by a creature. A few options here:
- Otiluke's Resilient Sphere: Stops enemies from targeting you directly for a brief time (until they dispel it). Good for running out of range when you expect you wouldn't have been able to otherwise.
- Fog Cloud/Darkness: breaks line of sight, you can now cast whatever other spells you want that don't require line of sight to the enemies.
- Greater Invisibility: Handy when you're already within Counterspell range and can't see a way to get out - now you can cast uncounterable spells from your invisibility.
- Globe of Invulnerability: Hard to cast when they have counters, easier with Contingency. They can still cast Dispel Magic on it, and as discussed you don't have the Counterspell numbers to stop that. But if they can't cast 6th+ level spells they will be rolling the dice on their Dispel, which is better than nothing.
Glyph of Warding is a lower-level spell that can accomplish similar things, but is restricted by cost and its stationary nature. You can make more than one of them though.
Staff of the Magi
Spell Absorption. While holding the staff, you have advantage on saving throws against spells. In addition, you can use your reaction when another creature casts a spell that targets only you. If you do, the staff absorbs the magic of the spell, canceling its effect and gaining a number of charges equal to the absorbed spell’s level. However, if doing so brings the staff’s total number of charges above 50, the staff explodes as if you activated its retributive strike (see below).
This allows you to absorb enemy spells (1/round) without giving enemies the opportunity to counterspell your counter. Doesn't help you cast your own spells though.
The Rod of Absorption has an almost identical mechanic (and is much more likely to be in the hands of a player than a Legendary Staff of the Magi).