I have almost the same situation as you have. I am making a portfolio of 10 different altcoins + bitcoin to break the risk.
But what I do is to check every single cryptocurrency thoroughly and read all documents about it before I do trade.
I would suggest to do a complete research on every single one of them before going for it.
Is that what you are starting off with initially? 10 coins?
Most of the ones I am interested in are large market caps, so I am concerned about creating a portfolio initially with just large caps. ETH is going to be my main squeeze, but I am unsure how else to diversify it in the beginning.