You won't need a lot of clothes, it's hot, extremely hot in the summer! You are likely to be uncomfortable in synthetic materials-forget the stockings.
Don't forget sunhat and sunglasses.
There is practically no night life (except a pub and a few restaurants), so you won't need your evening wear. There's one new hotel resort with a very nice bar/restaurant which may you may get refused entry to if you are TOO casually dressed, ie. Not just singlet, shorts and thongs or beachwear.
High heeled shoes may be uncomfortable in the heat. Loads of peolpe wear Crocs/Dawgs
Toiletries and Medical Supplies: All available in the pharmacy and small supermarket.
Sunblock spf 30+ is essential.
Photo Equipment: You'll definately want your best camera, an underwater one if possible, the reef is glorious.
Camping/Beach/Outdoor Gear: You'll need a snorkel and mask to see the reef, they are avilable for hire, but you might as well buy one if you want to go more than once.
There is a well stocked camping/fishing shop in the town.
If you intend to camp in the Cape Range National Park, be aware that there is NO WATER ON-SITE (there are 'bush toilets'), you have to bring your own, so you will need to have some large water containers and fill up in the town.
Miscellaneous: Bring EVERYTHING you are likely to need. Exmouth is a tiny place with very few shops and is so remote almost everything costs more than in Perth.
Basically you only need shorts/ t-shirts and swimmers.
Evening wear is shorts and flip flops.
everything about this resort is casual.....so you do not need to bring anything flash as you will look out of place.