Bitcoin mining requires high speed computers and efficient hardwares. Mostly it can cost from few hundred to thousand dollars. Bitcoin by default will make mining a difficult task with time (though miners can earn via transaction fees).
If you have enough time and money to invest in Bitcoins then go for mining otherwise buying Bitcoins is more easy.
If you are in US/Europe, buy it from Coinbase . Just sign up and start investing, you can invest from $100.
If youre in India, you can consider Unocoin, sign up, verify yourself with Bank details and PAN and youre ready to buy BTC