Hi! Croatia has a very good selection of wines. Basically there are two major wine groups, that of the coast(Istria and Dalmatia - Mediterranean) and the inland(Central Croatia and Slavonia - Pannonian basin).
Of the coastal white wines the most popular are Istrian Malvazija and Dalmatian Pošip, Pošip unofficially being considered the best Croatian white wine.
Among the coastal red wines there are several exquisite sorts that you should definitively check. First the Babić of Šibenik-Skradin vineyards, my personal favourite of all red wines, balanced and elegant, not sour, not sweet, perfect ruby-red dry wine to go down with any dish or occasion.
Second is Plavac Mali, a Dalmatian sibling of Primitivo and Zinfandel(all three are derived from an almost extinct Croatian vine called Crljenak Kaštelanski). The two most valued Plavac wines are Dingač and Postup.
As for the inland, it has varieties typical for Pannonian basin.
First and most popular of all whites is Graševina, Croatian term for Welschriesling/Riesling Italico.
Other notable white wines in the region are Rhein Riesling, Pinot Blanc, Pinot Gris, Chardonnay, (Gewurz)Traminer and Silvanac Zeleni(I believe this is Gruner Veltliner, although not 100% sure).
Of the inland red varieties, there are Frankovka(Blaufrankisch), Zweigelt and Pinot Noir as the three most widespread sorts, all good. :D
Edit: There is one other unique sort that you might wanna try out... Dalmatian Prosecco. It does not share anything other than name with Italian Prosecco. It is a very strong(20% alcohol) and sweet dessert wine made of dried grapes. I believe Port comes closest in terms of wine.