if you can find opportunities on your own then go for it, and never look for them in random online sites which can be misleading, malicious and dangerous to open since they can infect your system with some kind of malicious software to steal your bitcoins.

and those opportunities you find , you should consider prices, fees which are the two most important factors and the size of the orderbook where you want to buy and sell the coins to because you may end up bag holding and this is the most possible scenario in altcoins.