Centre bore on a E30 is the same as on a Golf - 57.1, you don't need any spiggot rings.
If the wheels are definitely from a E30, then they will fit perfectly fine, even with ET24 - that's actually isn't too bad, because my Borbet's are ET20, and you can still lower the car about 30-40mm with no probs.
Although, if you fit spacers, then you won't be able to go too low without rolling/pulling the arches.
P.S. Spiggot rings are simply plastic or aluminium (more expensive) rings, that sit on a hub to align the alloy to the centre bore of the hub. They won't be required if you are fitting any VAG alloys or the ones with the same centre bore as your car, but lots of aftermarket alloys have a bigger centre bore, so they can be fitted to load of different cars with relevant spiggot rings.