I am kinda new in this cryptocurrency and i wanted to buy some altcoins but i don't know which one, my friend said i should buy neo but i am not quite sure if it is a good coin or not.
No single altcoin is the "best altcoin".
I would definitely recommend diversifying your portfolio to incorporate various altcoins so that in case of a crash for one coin you are not just doomed. Spreads the eggs in multiple baskets, essentially, and you have a lot more opportunities this way.
For now, go with sia, doge, NEO and NEM.