If you are in Europe there are many like Bitstamp, Kraken and Bitpanda. I see Bitpanda as the easiest to buy as they don't need too much of a verification an email address plus a sms to your mobile number will give you access to buy up to 1000 Euro (in btc) per day.
Hope this helps. If you are from other parts of the world someone else may suggest other reputable exchanges.
Bitpanda. No more verification than an email address and a valid European mobile number where they will send a SMS to verify it's you. I don't know if they accept credit cards but it's almost the same as they accept, Amazon cards, Paypal, Skrill ,Neteller which are very well known payment processors.