The tricky thing is that there were different fashions for this kind of thing that changed dramatically over the course of the Middle Ages, the Early Modern period, etc – especially when you factor in the complicating factor of commoners getting richer than nobles by getting their hands dirty “in trade,” which makes the dividing line harder to enforce.
So for example, big displays of wealth could be very “on-brand” at various times, because nobles are supposed to be “magnificent.” This fashion obviously works in a context in which commoners either can’t afford to keep up with their betters, or aren’t legally allowed to due to sumptuary laws. At other times, understatement and the display of refined aesthetic might be considered the mark of true nobility – this fashion works in a context in which merchants, the rising bourgeoisie, etc. have tons of money but don’t have the social and cultural capital to know the “right” way to display it.
In general, I would say that some good rules of thumb for refinement are:
- Don’t Talk About the Price Tag: regardless of what the fashion is about the degree of opulence at the moment, one of the key attitudes of the nobility w/r/t money is that you don’t care how much stuff costs, because you’re supposed to be stupendously wealthy, generous and open-handed, and more concerned with refined aesthetics than commercial calculation. It’s not an accident that one of the oldest tropes about “nouveau riche” is that they constantly talk about how much various things cost, because they’ve still got that bottom line mentality going on.
- Know the Fashion, Know the Scene: one of the advantages of being a wealthy parasite who doesn’t work for a living is that you have a lot of spare time to do things like keep up with what’s in fashion and what’s not, what the trends are, who the best craftsmen are, etc. Especially in an aristocratic context where what’s fashionable is less decided by manufacturers and specialized press and more about what important individuals (the monarch, the monarch’s immediate family, the monarch’s mistress/mister, various long-time fixtures at court) are wearing, a lot of this knowledge is very personal and having a grasp of it is a sign that you’re close to the right people.
- Making Fashion, Not Just Taking It: of course, one of the clearest signs of refinement is that the noble in question doesn’t merely follow the latest fashions but makes them, bending it to their personal aesthetic. To give an example, “Beau” Brummell was a leading aesthete of his day and, thanks to his close connections with the Prince of Wales and his own personal force of charisma, changed the dominant well-to-do men’s fashion of the day from the fop (powdered wigs anf faces, knee britches, stockings, and buckled shoes, tailcoat, lace cravats, etc.) to the dandy (hair worn naturally, clean face, long trousers, white linen cravats, frock or morning coats).

