Trading is not just easy as you think. Its hard to predict in trading, so your money that you invest in trading is risky. So you need to be careful in buying a currency when you start trading. Before to start trading you need to watch and analyse or put a question in mind how it works to be success. You should also do research before buying and there are many buying signals for you.
Please do not discourage new comers. Unlike any other field trading has some possibilities to get profits if we are ready to show our efforts and dedications. Still I am not saying trading is a safe heaven to make profits. It requires hard work and knowledge. All the requirements of trading are easily achievable.
Practicing for free of cost is possible in trading too similar to gambling. But, we need to remember our experience so that we can make use of our knowledge at right times.
Wtf? Calm down there. Bitcoins are risky, altcoins are risky^3 and trading altcoins is risky^9. Don't be a naive fool and tell me that you don't think you're amplifying your risks by trying to get a quick profit.
To answer the OP
1) What should I start? Hm? Start with? mainstream coins.
2) Which platform should I use? Any large exchange, they all have the same possibility of being hacked.
3) How can I analyze the Altcoins? Whitepaper, Who is the dev?, is there a thread on bitcointalk? Is it just an obvious pump and dump coin?
4) Auto or Manual? I always do manual. I don't want someone else's strategy while using my own money.
5) From 1-10 how much is risks in trading Altcoins? 10. It's naive to think it's anything other than as risky as trading penny stocks. In 10 years it could be worth absolutely nothing or $100 a coin. You never know.