the best wheel spacer setup

hi,

i now own my first mk3 2015 blue Octavia vrs 2.0 tdi, 184ps dsg estate, getting the windows tinted, and alloys dipped black Tuesday, Wednesday  next week, but i want the wheels brought out a bit, closer to the edge of the wing, they are the 18" Gemini wheels 7.5j x 18 and a 51 offset, 57.1 center, i have put a plumb line down from the wing and with a tape measure from the line to the face of the alloy is 30 mm, so would a 25 mm spacer be best, or has anybody out there got any views on my matter

best stevie