The Mk1 GX, was a fairly late model, that had some of the interior and exterior styling of the GTI, but with the option of 5 doors and without the 1.8 engine.
The engine is sposed to be ok, but being only a 1.5 carb'd it ain't gonna be that quick.
Mk1's don't tend to look too good with massive wheels unless you remove the plastic moulded arches and get the arches rolled out.
Personally, I'd go for a nice set of 15inch retro looking wheels and a 40mm drop.
If you're looking for a cheap option, try some of the VW breakers and ebay for some Mk2 alloys, eg Pirelli P-Slots, tear drops, or if you're lucky, some LeCastalettes or Scala alloys or even some BBS rims.