Begin with three useful herbs
Choose herbs you regularly cook with rather than a large mixed collection. An Irish balcony may be sheltered from rain yet exposed to wind, so check the actual conditions at pot level. Notice where light reaches the surface and whether the balcony above intercepts rainfall.
Keep different needs manageable
Separate plants with different moisture requirements instead of putting every herb into one planter. Use suitable containers with drainage, stable positioning and room for root growth. Mint is easier to manage in its own pot. Check the needs of the exact species on its label.
Design the watering routine
Group pots where you can inspect them without leaning over a railing. Water according to the growing medium, not the weather forecast alone. A rainy day does not necessarily wet covered containers. Avoid runoff onto neighbouring balconies, and agree any fixtures with the property owner.
Harvest and reassess
Take modest amounts while the plants establish and note which herbs you actually use. Replace an unsuitable choice instead of expanding the collection automatically. A small, regularly harvested kitchen garden is easier to maintain through a busy week and easier to hand over during a holiday.