Can someone recommend a site to start trading altcoins? I'm looking for one that is trusted and has a good variety of coins.
I'd recommend you the yobit website, their aupport ia a little bad but they have a ton of alt-coins and adding new one as soon as they are published/announced. There may be some other webaited but I know about this one that has a vast variety of alt-coins.
I looked at their site (Yobit) and it's a little confusing, not very user friendly. If their support is shaky then I might stay away from that one.
Stay away from yobit. Too many shitcoins there, too much stuff you don't need and their site design is cancer.
Poloniex and Bittrex are fine.
There are things like c-cex, bleutrade, southexchange and whatnot, but I would only register there if you wanted to get a specific altcoin that you'll only get there.
Would recommend Poloniex, especially Bittrex. These two is easy to use and user friendly. These two has smaller fee compared to other trading sites such as Yobit that has very high fee.