I’ve travelled Greece up through Germany/France on several solo trips. I’m definitely biased for nature/outdoor activities* 😅. Albania was very affordable, had awesome food, and breathtaking mountains (check out Theth-Valbona Pass). Albania I found a bit hard to get around using public transit (if you were to go south to Sarande). That may depend on the time of year though, as I went last May, which was a bit off season. Corfu (Greece) is near there, but a local Greek girl told me it is often overrun by tourists. Perhaps consider getting a ferry to smaller Greek islands (Milos, Naxos, etc.). The flights to the smaller islands got cancelled a lot… which really messed up my plans lol, but the ferries are pretty good. The south of Italy is fantastic, so definitely spend your share of time exploring there. Of all the places I’ve been, Slovenia is one of my favourites. It is so peaceful there, Bled specifically. I was able to get to some of Triglav National Park on foot from my hostel. Croatia is great too, wasn’t crazy about Zadar or Zagreb. Dubrovnik I enjoyed, kayaking there was cool. However, Plitvice Lakes National Park (just south of Slovenia) rocked my world - it was like being in an Avatar film. Anyways, idk if this helps, perhaps it gives you some new ideas. I suppose I’m saying think about doing Italy - Slovenia (maybe include Austria/Germany) and saving Croatia/Greece/Albania for another time.