The Eurail website and the rail planner app should not be used to plan because they're unreliable and are only updated every few weeks. I'm not sure if they already contain the complete new timetable valid from 11 December.

It's better to use national timetables, or for international planning, the Deutsche Bahn planner. The SNCF website and app are not great (and that's an understatement), so for France I basically use the DB planner. For trains without reservations, check "Only local transport” under the Types of transport options. But only in France. In Belgium, Luxembourg and the Netherlands, only uncheck high speed services.

Check for routes via Lille, via Charleroi and via Luxembourg. You'll need one or maybe two nights, depending on how you want to do it.

It CAN be done-but an outlay of just 10€-if lucky that you are in the quota for TGV/France-is not overly much, or 6€ for a much, much faster trip on RENFE either. Plus that doing it your way makes the trip of course much longer and an overnite needed=cost of hoStel too. But perhaps you wanted to visit that city anyway as a kind of bonus.To add more insult_ just by incident I booked myself a flite-no luggage-for 19,99 Alicante-AMS on easyjet for march.

This is just out of memory-so double check what may have changed-certainly for > 11/12.

RENFE: 1/day regional tren Vlc-Bcn. Old stock, hard plastic seats.

Ev 1 or 2 hrs rodalies/Cat-Express to border with FR (POrt Bou-Cerbere).

IN FR there are also a few long-dist TGV bypassing Paris to Lille-or even Brussel-but RES for those seem very hard to get.

RES free trains there are labelled as TER and run via the old classic lines (that all trains used before these hi-speed lines opened): along coast till Avignon-Lyon-change-Paris, ev 1 or 2 hrs.

BUT I would suggest you aim for Geneva/Swiss (as Swiss prices are so sky-high you have more worth from a pass-and the views are much nicer too), TER from LYon-to Geneve-then SBB to Basel and then the overnight combo NJ/IC (NO RES as such needed for the IC-part=seats only, but expect an uncomfy nite, ending in AMS-just a few hrs late usually.

Inform yourself exactly on how these passdays work (till end of trip when started < 23.59) and I guess you will need to stop somewhere along FR coast there.

OR-but that will be very hard around Xmas etc.-find a cheap overnite FLIXbus between 2 points to cover the bridge.

RES for RENFE are a PITA-but as you live there anyway, visit its counter estacion, if needed.

You will never find this on any planner-have to break up in shorter segments (who would ever have thought of that?)-and for me bahn.com is best-can use many filters to satisfy your needs. (IF you know a bit of US commuter rail: it is about the same as doing the NO-East corridor via such trains=change much more often as direct on AmTrak)

The best way to plan is use a Railmap. The Interrail one shows with most routes. Then as the previous post says break the journey into shorter sections and use the without reservation function. If you can’t get anything shorten the section until you do but there are a some lines in Europe that only have compulsory reservation trains. Once you get out of Spain there are many options. You’ll get great value from your pass, meet locals and independent travellers that prefer not to be a sardine in a TGV. And you’ll see wonderful scenery. 

Planning your trip in one big strech usually gives weird results. Think of splitting it up in logical geographical, smaller stretches, and stick them together. Be sure to have some buffers, in case something goes wrong (delays, causing missed connections).

I really like using this trip planner for (theoretical) planning: https://hafas.bene-system.com/bin/query.exe/nn?protocol=https:&L=profi, combined with this railway map to see where trains can bring me https://www.openrailwaymap.org/.

For the latest real time results you should use the website and apps of the local transportation authorities. But beware of France, SNCF have the tendency to guide you into their TGV’s. With the French regions taking care of local transport (and regional trains) it’s easy to get confused.

If you would really want to get some speed for a minor reservation cost, and skip a lot of tight TER connections and a ho(s)tel stay, try to find a TGV from Perpignan/Montpellier/Nîmes to Lille. Reservations for 10 or 20 EUR via b.europe → But! Almost Christmas, so they might ‘ve sold out.

From Lille you have connection to local Belgian trains, being albe to bring you without reservation to Amsterdam.