"There are a lot of things you can learn if you are around securities over the course of your career, and you will find a lot of arbitrage opportunities. However, that probably won't be the primary driver of your investment returns.
If you are not a professional investor, then you should be extremely diversified and you should do very little trading. However, if you want to bring an intensity to the game, and you are going to value businesses, then diversification is a terrible mistake. If you really know business, then you shouldn't own more than 6 businesses. Very few people have gotten rich on their 7th best idea. You'd be much better off putting more money into your best idea. "