The line closest to you would be the best. Just push into the alleyway and not the main taxiway.
The taxi line in the middle is probably reserved for a much larger aircraft so there’s enough clearance between the gate area and the taxiway. Smaller aircraft would not be able to push or taxi until this larger aircraft clears out of the alleyway.
The line furthest from you could also be possibility if an aircraft is occupying the line closest to you. This would mainly be used for aircraft at the other terminal though.
I’m not an expert, but from looking at FR24 a bunch, some aircraft can push back on the main taxiway if there is not enough adequate space on the taxiway (i.e. other planes, “building” is too close). Wouldn’t recommend that though as you’ll hold up others behind you. If it’s quiet, go for it.