I used coinmarket.io to buy my coins and it worked really well!
is another exchange that has DGB, but it doesn't have as much volume as CoinMarket.io yet. This means that you might be able to find more extreme deals there, leading to bigger profits / more coins if you're lucky.
There is also the site:
http://cryptokopen.eu which sells DGB for a fixed price, using Skrill payments.
However there are rumors going about that the Skrill payment provider is bankrupt, or is near bankruptcy, so I'm not sure whether that is still a viable option. (At least until CryptoKopen.eu starts offering another payment processor.)