Hi Miklos
This subject has come up several times and I have harped on about my ideal layout - I haven't time to search for the discussion properly.
Basically, if you are playing music in the keys used for most Irish, Scottish and English dance music (without venturing into the flat keys of Scotland) I would recommend the Jackie Daly 12-bass layout on Han Speek's page, with one correction. Jackie has an E on the push on the last pair, not a G#.
The last pair is really a matter for personal choice, depending on what would be most useful for you. I like having a Bm push, so B/F# or B/C# (to give you a full octave in bass notes) would be my choice. Jackie Daly likes playing some tunes in B/C fingering, which is why he likes the E push (corresponding to a D push on B/C system). Others might like C#/G# for minimal playing on the C# row, or some flat options.
Cheers
S