I'd also recommend learning "Hochdeutsch" to begin with. Once you have a good level of German you can always learn to speak in a regional accent, depending on where in Germany you want to go/live.

There are several German dialects, and then there is "Hochdeutsch" (literally: high German) which is a bit like RP/Received Pronunciation in English. It's definitely best to learn "Hochdeutsch" which you'll hear in all the online courses, from the news speakers on national television (ARD und ZDF), on the radio (Deutsche Welle) and in all probability from the German teachers on italki, so there's no need to worry about that. :) Good luck!