My personal strategy is to hold 5-6 of the more well-known, long established coins like ETH, Dash, Zcash, Monero, BTC, and LTC.
Beyond that I'm only investing in projects where I know someone personally, or where I see that the token is not simply grafted onto a shit business plan. Especially if the token has value sources that are relatively stable, I will consider holding it.
That is not a bad strategy but the risk of your investment will depend largely of how much money you have allocated to the safe coins and to the risky coins if most of your money is in the most well known coins then the risk is low but if most of your money is in icos then your risk is higher.