Dandruff is a common situation. Discontinuation of oils and using an antifungal shampoo everyday for first week and then reduce the application to twice a week for maintenance. You should keep the shampoo at-least for 5 minutes on the scalp for it to act. This should solve your problem. However if problem persists, consult a Dermatologist for proper diagnosis and treatment and to rule out any other skin condition. Hope it helps you.
Next Steps
Nizral or Conaderm are good antidandruff budget shampoos but there are better products also.
Health Tips
You can consult me on Practo Direct for personal recommendations as on public platforms, I cannot generate a prescription.