Suffice it to say, every actor works differently. Laurence Olivier would put on his costume and when the wardrobe was right, he was in character. That sounds superficial, but it's true, and look at the results.
Building a proper wardrobe is like building a home. Indeed, you should think of it like a home, because it is something you're going to live in. It must be comfortable and suit all your needs.
When I do my own wardrobe, I try to wear a designer from each of the countries I'm visiting: Tom Ford for New York, Hugo Boss for Germany, Burberry for England.