There is no truly practical discount card for regular flights in Europe that I am aware of. You are looking to fly often and be aware that this comes at a price. That being said, there is a number of tweaks where you can optimize.

• First I suggest you get a very good understanding of which connections are practical in getting you from where you are in the Netherlands to where you need to be in Spain (I assume a pair of cities). Rome2Rio is great at this, but also Kiwi. With Rome2Rio it already gives you the non-flight transport options (but you have no way to specify dates), whereas for Kiwi the dates can be set (quite freely so) but you have to figure out about getting to the airport yourself.
• Try to avoid flying on busy dates, i.e. major holidays (Christmas, Easter, ...) or other events (trade fairs, conventions, conferences, ...) if you can and unless you intended to travel on these occasions in any case.
• If your likely itinerary is on a traditional carrier (e.g. KLM or Iberia, as opposed to low-cost), they likely charge more for one-ways and returns with a short stay (less than 2-3 days or a weekend day typically). A way around this is to nest your flights: have two bookings such that the return of the first booking is actually a month later, while the return of your first trip is with a different booking. Also the origin can make a difference, so it might be better to have most bookings originate from Spain or the Netherlands. Collecting miles with the frequent flier program of the airline might give you a free flight every once in a while, but cost-wise you are much better off booking cheap and getting less miles.
• Subscribe to blogs on cheap airfare and company newsletters to be aware of sales periods and offers. Especially Ryanair often has good discounts this way.
• Timing is crucial as well: not too late and not too far ahead. You will need to build some experience yourself on this. My rule of thumb is that if I know my dates and I see a good fare, then I do take it.
• Being flexible with dates and origin/departure cities helps too. (Maybe fly out of Germany or Belgium instead?)
• Savings can also be had by booking through the right channel (airline website vs. flight search sites vs. brick and mortar travel agents) and often means of payment (bank debit vs. debit cards vs. ...). For flights within Europe the website of the operating airline is typically my first guess. Sometimes flight search engines do offer discount codes.

There is no truly practical discount card for regular flights in Europe that I am aware of. You are looking to fly often and this comes at a price. That being said, there is a number of tweaks where you can optimize.

• First I suggest you get a very good understanding of which connections are practical in getting you from where you are in the Netherlands to where you need to be in Spain (I assume a pair of cities). Rome2Rio is great at this, but also Kiwi. With Rome2Rio it already gives you the non-flight transport options (but you have no way to specify dates), whereas for Kiwi the dates can be set (quite freely so) but you have to figure out about getting to the airport yourself.
• Try to avoid flying on busy dates, i.e. major holidays (Christmas, Easter, ...) or other events (trade fairs, conventions, conferences, ...) if you can and unless you intended to travel on these occasions in any case.
• If your likely itinerary is on a traditional carrier (e.g. KLM or Iberia, as opposed to low-cost), they likely charge more for one-ways and returns with a short stay (less than 2-3 days or a weekend day typically). A way around this is to nest your flights: have two bookings such that the return of the first booking is actually a month later, while the return of your first trip is with a different booking. Also the origin can make a difference, so it might be better to have most bookings originate from Spain or the Netherlands. Collecting miles with the frequent flier program of the airline might give you a free flight every once in a while, but cost-wise you are much better off booking cheap and getting less miles.
• Subscribe to blogs on cheap airfare and company newsletters to be aware of sales periods and offers. Especially Ryanair often has good discounts this way.
• Timing is crucial as well: not too late and not too far ahead. You will need to build some experience yourself on this. My rule of thumb is that if I know my dates and I see a good fare, then I do take it.
• Being flexible with dates and origin/departure cities helps too. (Maybe fly out of Germany or Belgium instead?)
• Savings can also be had by booking through the right channel (airline website vs. flight search sites vs. brick and mortar travel agents) and often means of payment (bank debit vs. debit cards vs. ...). For flights within Europe the website of the operating airline is typically my first guess. Sometimes flight search engines do offer discount codes.

If all of this is too complex for you even after some own research and trying, go for a good travel agent.

There is no truly practical discount card for regular flights in Europe that I am aware of. You are looking to fly often and be aware that this comes at a price. That being said, there is a number of tweaks where you can optimize.

• First I suggest you get a very good understanding of which connections are practical in getting you from where you are in the Netherlands to where you need to be in Spain (I assume a pair of cities). Rome2Rio is great at this, but also Kiwi. With Rome2Rio it already gives you the non-flight transport options (but you have no way to specify dates), whereas for Kiwi the dates can be set (quite freely so) but you have to figure out about getting to the airport yourself.
• Try to avoid flying on busy dates, i.e. major holidays (Christmas, Easter, ...) or other events (trade fairs, conventions, conferences, ...) if you can and unless you intended to travel on these occasions in any case.
• If your likely itinerary is on a traditional carrier (e.g. KLM or Iberia, as opposed to low-cost), they likely charge more for one-ways and returns with a short stay (less than 2-3 days or a weekend day typically). A way around this is to nest your flights: have two bookings such that the return of the first booking is actually a month later, while the return of your first trip is with a different booking. Also the origin can make a difference, so it might be better to have most bookings originate from Spain or the Netherlands. Collecting miles with the frequent flier program of the airline might give you a free flight every once in a while, but cost-wise you are much better off booking cheap and getting less miles.
• Subscribe to blogs on cheap airfare and company newsletters to be aware of sales periods and offers. Especially Ryanair often has good discounts this way.
• Timing is crucial as well: not too late and not too far ahead. You will need to build some experience yourself on this. My rule of thumb is that if I know my dates and I see a good fare, then I do take it.
• Being flexible with dates and origin/departure cities helps too. (Maybe fly out of Germany or Belgium instead?)

There is no truly practical discount card for regular flights in Europe that I am aware of. You are looking to fly often and be aware that this comes at a price. That being said, there is a number of tweaks where you can optimize.

• First I suggest you get a very good understanding of which connections are practical in getting you from where you are in the Netherlands to where you need to be in Spain (I assume a pair of cities). Rome2Rio is great at this, but also Kiwi. With Rome2Rio it already gives you the non-flight transport options (but you have no way to specify dates), whereas for Kiwi the dates can be set (quite freely so) but you have to figure out about getting to the airport yourself.
• Try to avoid flying on busy dates, i.e. major holidays (Christmas, Easter, ...) or other events (trade fairs, conventions, conferences, ...) if you can and unless you intended to travel on these occasions in any case.
• If your likely itinerary is on a traditional carrier (e.g. KLM or Iberia, as opposed to low-cost), they likely charge more for one-ways and returns with a short stay (less than 2-3 days or a weekend day typically). A way around this is to nest your flights: have two bookings such that the return of the first booking is actually a month later, while the return of your first trip is with a different booking. Also the origin can make a difference, so it might be better to have most bookings originate from Spain or the Netherlands. Collecting miles with the frequent flier program of the airline might give you a free flight every once in a while, but cost-wise you are much better off booking cheap and getting less miles.
• Subscribe to blogs on cheap airfare and company newsletters to be aware of sales periods and offers. Especially Ryanair often has good discounts this way.
• Timing is crucial as well: not too late and not too far ahead. You will need to build some experience yourself on this. My rule of thumb is that if I know my dates and I see a good fare, then I do take it.
• Being flexible with dates and origin/departure cities helps too. (Maybe fly out of Germany or Belgium instead?)
• Savings can also be had by booking through the right channel (airline website vs. flight search sites vs. brick and mortar travel agents) and often means of payment (bank debit vs. debit cards vs. ...). For flights within Europe the website of the operating airline is typically my first guess. Sometimes flight search engines do offer discount codes.