What is the definition of a winning portfolio? Everyone wants to build one but can everyone do it? Also, I'm sure the capital matters so those who are not as wealthy may not be able to achieve that?

With all these new brokerages allowing you to buy fractional shares, i dont think the capital matters anymore. You can build a "winning" portfolio on any amount (but let's not stretch the argument too much aka a $1 portfolio). I think with some (very) reasonable amount, say $10,000. You can build a portfolio that has like 50-60 companies in it (since you can buy less than one full share of companies like TESLA, APPLE etc)

I believe a winning portfolio is one that suits your current financial goals and risk appetite. Although it may seem easier for people to start investing with huge capital, the truth is that you can get started investing with even <$100 monthly these days. By doing it on a regular basis, it can work wonders in time to come. So get started!