Don't worry about the gauges just yet. There are limited options for power at the moment anyways.
Get a chip, get lowered, maybe an exhaust, and then maybe get a gauge.
There are no real good mounting solutions yet, but there soon will be.
42nd draft designs will probably release an a-pillar pod which looks nice, there will probably be a center dash/vent 3 gauge pod available soon, and I think there is a steering wheel pod coming soon too. Some people have already replaced the radio w/single din units and the extra space can mount a few gauges. The Audi A3 also has a vent gauge mount that will probably be out for the mk5's too(awetuning).
The boost gauge is nice to have, but it's only really useful if there is something wrong. EGT and oil temp/pressure gauges would be good follow on gauges depending on what you want, but really.....none of them are necessary at this time.