Booking Train travel in Spain, what site to use?

Check Seat61 for current info:
https://www.seat61.com/train-travel-in-spain.htm

I have usually used Renfe, the Spanish rail site.
If more comfortable working in English English, Raileurope is recommended by Seat 61., or Trainline.

This is where I would begin. https://www.renfe.com/es/en.

For Madrid to Barcelona I recommend Iryo, www.iryo.eu. Renfe's trains are also good, but their website is not always easy to deal with so it's much easier to buy a ticket from Iryo. From Barcelona to Girona you can either take an AVE train or a regional train. AVEs are faster, but should be booked in advance. So it depends on how you value cost vs time vs flexibility.

For Madrid to Barcelona, Iryo, Ougio and Renfe each run express services taking about the same time and departing from / arriving at the same stations. I'd use Trainline to get an overview of what is available on your particular date. Then book either via Trainline (supplement) or with the company which you prefer.

Hi all, thanks for the advice. I used the View from Seat 61 to understand the train systems and classes.
I ended up using the Renfe web site in English. We did an AVE train from Madrid to Barcelona in the Comfort Class (1st class) and was able to book seats facing each other with a table between us, just a table for 2. Had to look at all the cars during seat selection to find that particular kind of seat. For the Girona round trip from Barcelona I used Renfe again and was going to use an AVE train again, except the times weren't the most convenient. After looking at Seat 61 again and some Utube videos, the Avant train seemed just fine for a 39 min ride. I also found on the last car the only available set of just 2 seats facing each other with a table. There were only 2 or 3 pairs of these kind of seats in the 7 car train. We're also picking up a rental car in Girona to go to Figures for the Dali Theater and Museum and then over the hill for a night in Cadeques and the Dali House at Point Ligat. On the way back to Girona will stop at Gala's Castle (Dali's wife's).

SOME ADVICE ON THE RENFE site. Be quick, it times out. Use a different site to view the train times ahead. Do read the Seat 61 web site. Don't use autofill from your computer, this siemed to cause screen freezing. If the screen freezes, go all the way out, not just reload the page. Click the credit card/4payments button to pay by card. It worked fine. I always pay in Euro's anyway, however they had a high exchange rate and a surcharge if you pay in US dollars.