Unless you have got money (and can by containerised plants that are
already there) gardening is not a quick fix. Take you time and see
things develope. 5-7 years would see a good looking yew hedge, a good
dense beech or hornbeam.

What kind of soil do you have?
How much time do you have to cut it?
What do you want Solid hedge all year, evergreen or are you ok with a
deciduous hedge which is semi see through, during the winter?