Hi and welcome to the steemit community, all the best for your experience here. I put together some articles that may help you on getting started on the platform. You can read "Common Mistakes To Avoid" & "Sell your Upvotes For Extra Cash". Hope you will find it helpful and good luck.
To answer your question I use both Poloniex and Yobit, here is ehy if you are interested in reading - https://steemit.com/cryptocurrency/@cryptoscout/poloniex-and-yobit-why-i-trade-like-this