Which books are you using? You could be a vHuman and take the magic initiate feat: that allows you two damaging cantrips (Eldritch Blast, Fire Bolt) that will stand you in good stead. Suggest Magic Missile as the level 1 spell if your focus is damage.
I found Shatter (2d level spell) to be Underwhelming, but it was now and again a useful spell at low levels.
Magical Secrets at level 6: Fireball.
Level 4 spell: Wall of Fire. Depending on how you shape this, it can be very nice but you have to maintain concentration.
When you can get it: Synaptic Static. (5tyh level spell)
Magical Secrets 10: Animate Objects. (5th level spell) Surprising amount of damage) or
5th level spell: Cone of cold: this one does pretty well, resistances considered.
Steel Wind Strike: lots a damage. spread out over five targets
When you can get it: Circle of Death. (6th level spell)
When you can get it: Disintegrate: level 6 spell, need 14 lvl magical secrets.
When you can get it (lvl 13): Prismatic Spray. (Level 7 spell, it is on the bard list (at least in Tasha's) and OMG can it deal out the damage to a crowd. Problem is that it takes a long time to resolve if you hit a lot of creatures.
When you can get it: Delayed blast fireball. (7th Magical Secret)
When you can get it: Meteor Swarm (9th Magical Secret).
As to counterspell: get it. Psyren is right, it's a good choice.