Localbitcoins, and bitcoin ATM's are easiest. On Bitstamp you can again buy bitcoins with credit card, but if I remember right fee is rather big, I think bank took me $40 for $250 purchase. It's not Bitstamp's fee, its my bank fee. Also I bought with local exchange from my country, payed with bank wire, and took me around $20 for $250 purchase.
All of the website that has feature of buying bitcoins using credit cards has a big fee the best thing to convert money into bitcoins is to find a legit seller not in the website because website is a business it has automatically have a fee when you transacting but when you buy in people you will get a discount.
every time check both localbitcoins and paxful prior to making another trade elsewhere. right now, i am using paxful for changing bitcoins to american express serve and the exchange is nearly even money. I did a small one recently as an example and got $4.01 of serve for $4.18 of BTC. That does not account for the 0.0005 fee to move the BTC in, but that is nothing.
i wish i knew what was up with these guys and squarepay. i cannot bring myself to do it, but they often offer 500% for BTC to squarepay. I do have a squarepay account, but have no idea what their policies are on reversed TX's. if it was paypal, i would expect a near immediate reverse on a payment with a 500% pop, serve does not allow reversals. there is either a scam there or they have a shitload of btc that they want to unload.
alos, paxful allows almost anyone to post a trade and use only the built in escrow. localbitcoins wants a $400 deposit in addition to the amount of the posted ad. so, if i want to post a paxful ad for $50 BTC to whatever, i only need the $50 in btc in the account, on localbitcoins i would need $450 in the account. that means a lbc user has a little more to lose scamming, but if you use either site right, you are fine, since both sites hold the funds in escrow until you say to release them.