How many cryptos should Ihave in my portfolio? Are there one recommended diversification ( like having 3 or 4 coins) ?
It depends on you. but after 10 it is going to be hard to follow each of them fundamentally and also technically. I am investing 6 cryptos at the moment. I also don't recommend you to invest 1-2. Never put all eggs at the same basket.
An amount between 6 to 10 coins seems like the sweet spot, if you follow fewer coins like that then you are probably missing in some of the action the market is giving but if you follow more than that then you will probably need to make trading your main activity and many do not have the time to do that because they have jobs and other responsibilities to attend, besides if you like to follow the news of the coins in which you have invested it is going to be very difficult if you are following more than 10 coins.
However that does not mean that you need to follow the same coins all the time, you can change the coins you are following depending in your criteria, for example if a coin that you were following losses too much volume you could drop it for a new coin with more volume.