Just try to not to buy like tens of different coins, try to pick MAX 10 coins you like and see succeeding in the future.
I have tried to hold 15+coins and things get messy really soon, cannot keep track anymore.
you are right,, if we talk for long term hold 10 coins is good,
but, if we talk about short term i think you can add more,, but should be less than 20 coins,,
and to track my portofolio i use blockfolio, its really help me