Hi there,
What exact dates will your trip be on?
For example, for great tips, the grand Museum of Catalan Art is free on Saturdays from 3 PM, and lots of museums are free on Sunday afternoons.
Otherwise, if you plan to visit at least two Gaudí sites, I recommend a combo pass or ticket. It’s already expensive, but it’ll cut the cost a bit.
Palau Güell, by Gaudí, is the cheapest at 12 €.
I was in Barcelona at the end of January, for the 4th time. Here are a few visit ideas:
https://www.lasourisglobe-trotteuse.fr/barcelone-en-3-jours/For accommodations, here are some recommendations:
https://www.lasourisglobe-trotteuse.fr/ou-loger-barcelone/For eating out, you can use The Fork app to get discounts, but it rarely works if you’re alone.
After that, if you avoid La Rambla, there are plenty of tapas bars at good prices.