I have never used Bento, and I understand it is a very capable program. But, having used Filemaker for many years, I prefer to formulate my own databases with the capabilities I specifically need.
Your challenge of tracking 50 people with varying investments would start with two tables, one for the people and one for their investments. Showing the person's investments with the use of a portal on the person's layout would give you a look at the history of investing and then in an investment layout you would have ways to sort all the investments.
I suspect there's more to your needs, but this simple solution should easily manage them as per your brief example.