Hello,
i am into cryptocurrencies for some years but last month i am trying to trade in Poloniex for fun. I can tell you what i did.
It was very boring for me to just read theory without any practice so i desided to jump in the deep water and just start trading BUT with VERY LITTLE ammount of money. Some money that you can lose for a day and dont care (for me it was ~ 50 $). When you start trading you will learn really fast a lot of things about how the market works, how the platform works and the most important thing - how your emotions works in that situation.
Be very careful about this :
At the beginning you will be very careful about your decisions and you will probably make some profit (maybe) Don't scale it in your mind!!! Just don't deposit bigger amount because you are going to lose it. First two days i have made 7 % profit and i was thinking " Shall i put some real money and try with that " but than the price dropped a little bit and i was back in reality again
.
Just play with amount that you can lose without problems and don't let some profit blinds you.
The depressive part of the story is that no matter what you do, what you read and how good you are in this you CAN'T predict the future (market). But that doesn't mean that you can't make some profit of it and some fun.
About the coins : It is definitely better to chose to trade something that is famous enough and a lot of people are trading it. I personally trade DASH, Ether and Monero.
Good luck!
P.S.
Someone mentioned that Poloniex want ID verification. I am trading there, deposit and withdraw for some time and i have never been ask for ID. Is it only if you trade with leverage or what ?