It's getting harder and harder to be profitable in crypto world. The more players are coming onto the scene the more effective the markets are. But it's still possible to be profitable, it requires a lot of money/big capital though.
Is Arbitrage possible on Crypto market? Yes, but it requires a lot of effort to establish profitable yet effective trading systems. From my experiences the biggest obstacles are fees for withdrawals and big capital requirement on the begging.
There is only one proved sort of holy grail in trading. Compound interest "Compound interest is the eighth wonder of the world. He who understands it, earns it ... he who doesn't ... pays it." this quote is awarded to Albert Einstein. Who knows if ...