I have a mild form of epilepsy but have had seizure only from sleep deprivation except one time from a stupid overdose of aMT+MDAI.
Have had countless K-Holes without any issue, but please understand this is not medical advice but only my personal experience.
Your mileage may vary, meaning I'm not saying it's safe for you or anyone with epilepsy to take Ketamine.
GHB and GBL may or may not induce seizures directly, but remember that some drugs can induce seizures directly, and other drugs can induce seizures if you take it often, develop a tolerance and then cease consumption without a slow taper.
This is true for Benzos, in instance, and GHB/GBL also do have GABA receptor activity, therefore I would absolutely recommend against taking this regularly.
You also mention taking Methamphetamine, and if you are epileptic I would recommend against taking it, as it is a direct cause of seizures and also because it promotes behaviours that are also cause of seizures like sleep deprivation, not eating and drinking enough, overexerting and overheating oneself.
The research about Ketamine and Epilepsy:
Ketamine: A Convulsant? Madhuri S. Kurdi, K. S. Sushma, R. Ranjana, and P. Bharath Kiran
Effects of ketamine in epilepsy. Celesia GG, Chen RC, Bamforth BJ.