If you want to: retain some semblance of comfort, lower no more than 10mm, achieve even arch gaps and not spend a lot, you could try:-
HR 29261 springs with Bilstein B4 (oem damping profile, but gas charged)
Or if you want slightly more poise and stiffness:-
HR 29261 springs with Bilstein B6 (MK6 flavour, approx 15% softer than MK5)
I wouldn't go for B8 unless lowering 30mm or more. The extra droop of the B6 (stock damper length) is useful for traction over big bumps, undulations and kerbs.
Racingline kit: Feels great initially but the transition from soft to firm is too abrupt for my tastes. It's also too soft when upping the pace on bumpy B roads, to the point of causing front arch fouling....with stock wheels and offset! Pants.
The one thing the MK5 needs for composure and comfort over bumps is suspension travel. Drop them 30mm or more and they just ride like crap imo, but it all depends on what your local roads are like. Some of us are blessed with German grade tarmac, and some of us have to put up with Bulgarian farm tracks.