Where to live? A few ideas please.

You might like to have a look at a little village that is about 10/15 mins drive from the sea, still very Spanish with all local amenities, doctors, health centre, farmacia, butchers, bakers etc. It is approx 30 mins from Alicante airport and about 40/45 mins from Murcia airport. It is called Formentera Del Segura, It is also near to main resorts such as Torrevieja (20 mins drive)and Guadamar (more refined) but far enough away for the tranquility that the village has to offer. Have a little time to research the area you might be pleasantly suprised, especially what you can get for your money. Hope this is of some help to you. Good luck with your search, but I think this may be the final place that you have to look once you have seen it?

Your choices are  greater (and better) if you are prepared to live well away from Brits. For example,  Extremadura has plenty of agricultural opportunity as well as wonderful cities. The Guadiana valley, specifically Dom Benito, is one of the up and coming agricultural areas, as is Almendralejo. They have huge water resources. Soil type isn't important, as you can rip your land with a bulldozer and add whatever is needed, eg dolomite, calcium. But water is pivotal. Best is to drill until you find it in quantity. If you want a few cows, goats, chickens, etc I would go for at least 3 ha. At that size you start getting a bit of privacy. Buy somewhere with a house, as the planning permission regime will take years, even if all goes well. Entry level for you want for is about €300k. 

I would agree with GuyT about buying somewhere with a house already built, even if it needs reformed.  And as Floella said, you need a minimum amount of land to build.  Here it is 10,500m2 for an existing plot of land, and you can only build on 2% of that - if you get permission to build at all.

I was wanting to build in the countryside and found a plot of 25,000m2, which I then thought I could divide into 2 legal plots, and my friend and I could then build two separate houses.  However, I spoke to the town hall and they said that if you are dividing a plot then the minimum size becomes 25,000m2, instead of 10,500m2.

So just make sure that you speak to the local town hall before buying land for building - or better still buy an existing house and make sure it is fully legal.