Lucky for you, Mango and Zara is based out of Spain, so to fit both your taste, your budget, and have something different to wear everyday of the week won't be a problem as they have many reasonably priced items and different forward-thinking designs available.
Are you looking to purchase clothing that are unique to Madrid? As I can list you some of the brands that showed at this years Barcelona and Madrid Fashion week, who also have a boutique or retail outlet in Madrid... Loewe, Roberto Verino, Victorio&Lucchino, Adolfo Domínguez, and Elena Benarroch are also based out of Madrid.
Just stick to these streets: Goya, Velázquez, Jorge Juan, Serrano, Castelló, Príncipe de Vergara and Ortega y Gasset, and you'll find some unique, one of kind boutiques that are unique to madrid or spain.
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