There is different type of altcoins even if we can indeed speak about casino.

However, we can look at some parameters:

- How old is the coin?
- Was it attach overtime and how did it evolved to prevent such attack again?
- Does it have an active development community?
- Does it play the marketing part at 100% in order to attract people or is it reinforcing it's technology foundation to make sure it will stay overtime?

Bitcoin is a reference. 50% in the portfolio is great. Then you can probably put 5% here and there. I would keep 10-20% for highly undervalued coins such as Feathercoin for instance.