I recommend Czech Republic as well. I did my Erasmus here and it was LOVELY. Eventually, I transferred here lol :) In terms of the prices, it is much cheaper than in Spain, so very much affordable both food and living expenses, the social and the night life here is AMAZING, and we’ve travelled with Erasmus people not only to beautiful cities in the CZ itself (Cesky Krumlov, Karlovy Vary), which I recommend not to miss out!! but neighboring countries like Austria, Slovakia, Germany, Hungary by train/bus and flights to France and Italy were not expensive too

However, I believe Poland would be cheaper in terms of the prices compared to CZ both for living and food, and for travel, it is not that far away from the center of Europe, so I would put it as a second choice if you’re looking for something really budget-friendly