If you can live with an 11-36 10spd cassette, then this is the cheapest possible setup: the 5700 shifters + 9spd mtb/trekking rear derailleur from shimano (same cable pull, so no roadlink necessary).
If you need smaller gears: see above :)
edit: +1 on compressionless brake setup! makes a LOT of difference, much fewer readjustment necessary than with normal wire-based cable outers
If you can live with an 11-36 10spd cassette, then this is the cheapest possible setup: the 5700 shifters + 9spd mtb/trekking rear derailleur from shimano (same cable pull, so no roadlink necessary).
If you need smaller gears: see above :)
edit: +1 on compressionless brake setup! makes a LOT of difference, much fewer readjustment necessary than with normal wire-based cable outers