Definitely a good idea to pull some money out of other investments to spread into bitcoin... especially if you had taken them out of other altcoins. It may be exciting now... especially seeing that the price has been on a slow, but steady decline, that maybe we'll see a slight explosion or atleast some sort of new peak in value. But its the same idea with any other investment, if you put moree money in, you have to be comfortable with losing that investment. If I were you, I wouldn't get too excited or impulsive about throwing more capital into your investment, but to each their own.

Nevertheless... its always good to put your eggs in different baskets, and in the case where bitcoin or any other investments you may have shoot up in price, you are a wealthy or wealthier man Yet if the opposite happens, you will still have capital in other places. Keep doing research and best of luck to ya!

There is no specific amount that is  "enough"... it is whatever you are comfortable with in terms of the rate of it's growth and how much you can potentially lose.