To invest in watches, one must behave exactly as a "traditional" investor would, that is, make clear choices. And these concern the investment horizons. As you may know, there are different "profiles" in stock market investments. There are short-term investors, the so-called "day traders," and long-term investors - to quote a very famous one, Warren Buffett.
The former operates on the market continuously, chasing trends and bubbles - and trying to speculate on them (and remember, there is no negative meaning in this term). So, to make a practical case, they try to buy watches that are "bullish" right now, to put it in stock market terms and hope that their trend doesn't change. That is, they might buy a second wrist Rolex Submariner and try to resell it at a higher price a few weeks later, based on their perception of the market trend.
On the other hand, the latter tend to make few transactions and buy goods that are not in great demand at that moment but may soon become so. Indeed, if they are in a recession (the so-called "bearish" market), it is even better. So this kind of investor focuses on watches that are not fashionable but have the right characteristics to represent a good return in the future. In the case of watches, a stable price, an essential but undervalued brand, the presence of exciting complications. These investors are the ones who foresee market developments without chasing it - and so right now, they could buy watches from companies such as Girard Perregaux, Bulgari, and Piaget.
So, first, you have to find a profile and then operate within that profile to achieve your goals. And to do that, you have to develop knowledge and expertise of the watchmaking field that goes beyond that of the simple watch wearer, especially by continuing to follow the market and its evolutions.
The beauty of investing in watches is that - except in exceptional cases - you can wear your investment on your wrist and enjoy it, which is challenging to do with a bunch of gold coins or bearer certificates of deposit.