None. A common man should be an investor and in fact many common man in the US have 401K (pension plans) which makes them investors, many people (like myself, a classic example of a very common dude) have some stocks or funds. The message here should be that the common guy should get at least a minimum of financial education. There is not "an investor type" and a "common guy", there are simply different degrees of knowledge and investing ability.

One of the main problems I have seem is that many common people have associated the idea of investing with gambling, even they use these as synonyms. This is the confusion we should address.