The drain bolt should have a fibre washer fitted, oil does tend to leak along the threads and without a fibre washer can leak. As regards gaskets I make my own from gasket paper which can be bought quite cheaply off ebay various thicknesses I use 0.40mm for most gaskets but thicker for the rocker cover gaskets, and use a thin smear of grease on both sides of the gasket, I have been doing this on both my A7 and A65 for a while now and have no oil leaks from any gasket that I have fitted.