Investing in ICO now is very risky. It is not June or July.
So investing into only one ICO will almost definitely bring you down.You need your Expected Return to be higher.
I would select at least five.
Also, consider keeping 20%-40% in BTC/ETH.
All this does not actually depend on the amount.
In my opinion, ICO's should take no more than 15% of your portfolio.
There are lots of good perspective altcoins to look at, and they re less risky than ICO's