Hi Leah,
Seizures are fairly commen in dogs, at my clinic we have quite a few dogs that are on medications.
Was this your dogs first seizure? How long did it last? How long was the postictal stage (time after seizure where they will seem confused, dizzy, wobbly, etc)? Did your dog loose bladder control?
Usually medications are not started after just one seizure. Usually they are started when it becomes repetitive or when they experience sudden cluster seizures.
The main go to medications for seizures are phenobarbital and zonisamide. Both of these are the top choices by the AVMA.
As with any medication it is recommended to do bloodwork prior to starting - to get a baseline. Then re checking the bloodwork 2-4 weeks after starting to make sure that organ function is good and that your dog is tolorating the medications. This will also decide if your dogs dosage needs to be changed. While on these medications the bloodwork should be done every 6 months.
Seizures can happen for a number of reasons, epilepsy, toxin ingestion, tumors, etc.
Epilepsy is diagnosed by ruleing out the other options- this can be done with bloodwork, X-rays or even a CT Scan.
Keep in mind your dog will still most likely have seizures, this will not "cure" but will help suppress them.