On a budget, weigh it — Dubrovnik Museums Combined Ticket isn't cheap for what it is.
~€18–25 multi-site
Genuinely good value if you intend to do three or more civic museums, turning individually pricey entries into one reasonable ticket. The honest catch is most visitors realistically do one museum and the walls, in which case it's wasted money; only buy it if you're a committed indoor-culture day or a rainy-weather hedge.