And how to know if what is the best altcoin to choose to have some profit?
Do some research on a particular altcoin that you want to trade with. Don't just follow what others are trading. More often than not, they are just feeding you for some speculations.
I can suggest to OP Better to go with bitcoin trading in LBC. LBC account can buy at market place threads, Post your topic at there as mentioned as you need LBC account and Start trading.