Scotland have a 1-0 aggregate advantage - but I'll be honest I haven't watched many games in the tournament either. Greece's chances of beating Scotland are probably lower - that's because Scotland are playing at home. If you're going to bet - I think you'll know which team is more likely to benefit you in that match, but don't go all in there.
I think there are a few other games you can look at as well. I don't bet on teams I don't know - I don't mean teams I don't know how they've performed. So - don't force a bet if you're not sure about the team that's going to play, save your budget and bet on the team that's likely to be the favorite to win.
Yeah, we lost when we played against Scotland in Karaiskaki, I highly doubt we'll win them in their home, judging by that, as bad as it may sound, perhaps it would be better if I bet on Scotland, even if though they're playing against my country. I'm certainly not going all in on something I'm not quite familiar with, but I might as well place a small bet over not taking part at all.
Some options I'm considering is
Georgia vs. Armenia,
Serbia vs. Austria,
Belgium vs. Ukraine,
Portugal vs. Denmark and possibly a few others as well (the bolded teams are those I'm considering to support). Perhaps I'll look into more betting strategies as well, over/under etc, but that's the first plan I'm going for. Any thoughts?