The most useful types of medicines are
Analgesics(simple, compound and non-steroidal) for both adults and children.
Antacids
Antibiotics(mainly penicillin based or macrolides)
Asthmatic drugs
Anti-helminth
Anti-hypertensives
Allergy drugs
Anginal meds
Eye medication (antibiotic and glaucoma)
Emergency meds
Iron preparations
Malaria drugs
Skin ointments
Vitamins