I started on CEX.io not too long ago. It is the only/easiest exchange i could use to get my USD turned into BTC. I am able to send from PayPal > PayPal PrePaid MasterCard > CEX.io for 3.5% i believe. If i ass $20 USD in to CEX.io It only cost me about $21.50 (give or take) but thats a rough example. I started with $20 with at the time was about .02 BTC and with CEX.io I was able to "Buy and Sell" Trade upto about .04, then I Started margin trading Bitcoin on there and got to about .06 BTC (all within a month, for a brand new beginner) Then I went BTC to LTC and arbitraged the LTC to BTC-e when it was profitable at any given day or time, and then bought back to bitcoin, and Sent it from BTC-e to Poloniex. My main trading place now. Its easier to make money (or lose) on smaller valued Alt Coins, with more market movement.

I cannot use Tether.io for other Exchanges, so really my only way to buy BTC is throught CEX.io....