As Task said, the risk of holding HBD is that the price of HIVE goes to zero.
When it comes to the best way to convert fiat to HBD, your best bet is to buy HIVE off an exchange, transfer it into your account and then use the internal market to buy HBD with your HIVE.
In terms of getting to the internal market, I recommend using the PeakD front-end.
Go to your wallet, scroll down to the HBD section, click the dropdown and then select Market:
This will take you to Hive's internal market where you can trade HIVE for HBD at a good price.
Do it in small chunks as the liquidity isn't high.
RE: HBD is changing the algorithmic stablecoin game