what do you want with your bitcoin after you have? is it for trading, holding, or playing gambling? because you need to find what you want. it is easy for just buy but after that, what we want to do? if you want trading, then i can give advice to go at poloniex, bittrex, kraken, and else. make an account for each of sites, deposit some amount for start trading.

there is no minimum amount of bitcoin to start but i think you need to have at least 0.003 btc to start trading, less than 0.003 btc, you only use it for transaction fee. if you don't have knowledge about trading, then i suggest to you to search more info so you can start your first trading.

the best from everything i suggested, holding bitcoin is really work for you. you don't have trading, gambling and else. just hold your bitcoin until you see the best price so you can sell your bitcoin for making profit.