how many different coins i will buy for trading?
is it good to buy and sell 1-6 different coins or just stick to 1 kind of coin?
what coin and what was the best coin that i can be hold for a long time that give me good profit. can i have your suggestion, thanks and gobless !

Well never stick to one coin,you never know when an altcoin crashes,if you invest all your money into one coin and unluckily it crashes then you go bankrupt.It is always better to invest partly in different coins.
And coming to what coin you should buy,that is totally up to you there are many coins out there that can make you a good profit.So take your time and do your research.