Some orchids have water-storing organs, and some do not. If you have a type of orchid that has the ability to store water, such as cattleyas or oncidiums, you should allow the orchid to completely dry out before watering. If you have a type of orchid that does not have water-storing organs, such as phalaenopsis or paphiopedilums, you should water the orchid before it is entirely dry.
I think flying with the plant would be a challenge. Could you purchase one when you get there? Also, you need to check about bringing live plants into Spain because they have different rules for different countries. If you are giving the gift of a keiki or a cutting, that can be really challenging to grow for a beginner as well. So I’m not sure if that’s the best option. Honestly I think your best option is to contact this society and ask them what reputable growers they would recommend. I hope this helps! – Mary Ann