Hi, I am Polish GA pilot, fly a lot IFR/VFR, Poland, Czech, Hungary are easy going, but make sure they have fuel where you go (in Poland it may be difficult to get except ca. 10 major airports, but it is cheap), for Poland there is a great website -
Portal | dlapilota.pl, Czech Republic is probably easiest for pilot, if you consider Slovenia and Croatia they are friendly and nice with cheap fuel, Romania is very difficult (for VFR you need prior permit before even overflying) and veeery expensive (e.g. EUR 250 for handling and 1 day parking i paid in Cluj Napoca),