Look at the way of how you want to buy cryptocurrency and then you'll search the right exchange. If you want to get btc with fiat, no problem, many exchanges accept this option (CEX.IO, Coinbase). If you're going to spend your altcoins for new bitcoins, that's another question, go to professional trading platforms like BitMEX, and take advantage of each trade you make using leverage or stop limit. In case you just want to acquire cryptocurrency for saving, you may not deal with exchanges but go P2P platform or even easier - to ATM (depending on your location). Check also the possibilities to buy with online wallets like PayPal or Payoneer. So you see there are lots of options.