Diversification is always been recommended if your budget permits you but if not or only limited then its up to your own choice because success in investment will really vary on how you do handle up yourself on these kind of situations. Diversify while you can but be wise on taking such step.
Yes, but in the end still depends on how we looked at the situation. Sometimes I'm going all-in to a certain coin that I believe will be potential if I will keep my patience waiting for that day. Diversification is good but that's not my top task. Maybe between 2-3 coins but mostly, always going all-in.
Whatever our decision, to diversify or not, we just need to put effort into how can we manage our portfolio properly in the long run.