For me best broker to trade crypto’s is Coinexx. I personally trade with them. And so far I’ve had the best trading experience.
I have traded with LMFX for my trading so I can suggest only this one if anyone is interested. Otherwise you have complete Internet to research for good one.
Don't confuse brokers with exchanges. These mentioned here are all exchanges and that's the whole beauty of the cryptos. You don't need a broker, you get to trade directly on an exchange. Unless you're trading really large sums then you might want to consider finding some OTC (over the counter) brokers. You are your own broker there, no middleman and you trade directly with the other traders. I'd say it's a great way for beginner traders to learn how the markets work without spending plenty of money. The only thing that most of these exchanges lack is appropriate customer support. You can get to wait days or even weeks (and sometimes even months) to get a reply for issues that are directly caused by bugs on the exchanges - like missing deposits etc. If you trade bigger money, I'd say try to find some that can offer you a kind of VIP customer support - I think the only concern after the liquidity is to get the support as soon as you need them so if there's an option to pay for it extra I'd say go for that, it should pay off quickly. If you want something close enough to what can be called a "broker" that would be the Coinigy app where you can get a more user friendly interface and trade from there on multiple exchanges all at once. There's also a free software called QT Bitcoin Trader which you can install and connect with a number of particular exchanges - not the best solution but it's an interesting tool to try as well.