How many cryptos should Ihave in my portfolio? Are there one recommended diversification ( like having 3 or 4 coins) ?
it really depends on how much money you have in your pocket or wallet, may be big or small, as long as it does not belong to your savings, you should invest money that you are willing to take risk, because crypto trading is not that unstable in terms of price because of the volatility of its market price, some even invest their money that came from loan, if you are well enough to trade and knows the ins and out, you can invest as much as you can, but it is still best to invest money that you are willing to loose in case of a dump.
Even if you have so much in your pocket, it is always advisable to go with the number of cryptocurrencies you know you can handle at once. Sure, for long term investors, the ability to hold as many as possible will always be there anyway as long as they believe in the long term of the project they are holding which is something that is necessary to know before even investing into any project.
In this case, they can as well just build up their portfolio; allocate certain percentage of resources to this portfolio as the case may be. So at the end, it just personally depends on you and for sure, your pocket will also determine a whole lot as well.