which coin is good to invest for a long run after bitcoin? I do not have much knowledge also tell me best exchange to buy coins.
Go to coinmarketcap,
https://coinmarketcap.com/ and look for the number 2-10 coins after bitcoin. That is the safest bet if you really wanted to invest for the long run. When you say long run though, it means at least one to two years of holding on it, so just prepare yourself, specially there will be lots of ups and down along the way so goodluck to you.