There's no like standard recommended percentage, but it's always a good idea to diversify more depending on how much value you're holding. Let's say for example you're holding like $50, then there's almost no point in diversifying with such low budget. But if you're holding like $5000 or so, it would be best to diversify.

I think you're holding too much OmiseGo in my opinion. Good tech, yes, but I wouldn't risk as much as 30% on it. I suggest using a 50-10-10-10-10-10 ratio of cryptocurrencies instead, with 50% bitcoin. But it's up to you.