If you come from Hungary, you might want to do the customs on LRAR (Arad). As far as I know they used to have AvGAS available for GA, not very cheap tho .. about 2.5 EUR / liter, but better call and ask for availability.
Fees are about 30 EUR / landing, more information on their fee structure you can find here:
International Airport Arad
From there you can indeed visit the grass aerodromes that belong to the AeroClub of Romania. You can go via Sibiu, then to Craiova (LRCV) for customs before entering Bulgaria and AvGAS (call first)
About us
Other route that you can consider is via Sibiu - Brasov (Ghimbav) - Bucharest (Clinceni or LRBS if you'd like AVGAS and clear customs. LRBS fees should be about 50 EUR. AvGAS is availabe from TotalAir, but call before you arrive):
Aeroportul Internacional Bucure_ti Bneasa - Aurel Vlaicu
They are both nice routes with mostly mountain landscapes and valleys. Let me know what it would be of more interest to you and I'll try to find a nicer route. Also, where in Bulgaria is your final destination?
VFR flight is pretty straight forward, fill a flight plan and take-off. You can now fill the FP online at
Login (needs registration - it's simple, you just need a valid email address).
You should indeed keep your eyes open for glider activity near aeroclub's airfields and military activity in south. You will probably be in touch with the military on 130.00 (Rubin Control, Topaz Control, Onix Control depends on where you're flying, but they all share the same freq.) They will advise on any traffic.