Personally I'm not a fan of RTV silicone in addition to gaskets. I recently rebuilt my A15 and didn't use any sealant on the sump. Cleaned heaps of it off from the last work done though. It was all over the oil inlet screen.

No leaks that I can see. The rubber seals that go over the main oils seals bedded in fine. The cork gasket you just need to get the tension on nice and even and be careful not to over tighten. It's easy to extrude it and ruin the seal.

I was a little unsure about the paper gaskets since they're so thin, I used a small amount of form-a-gasket, a liquid sealant on them. The only problem I had was the oil pump leaking because I didn't get all the old gasket off properly the first time.

I generally use plain old engine oil for assembly lubricant. I try to work on the principal only add stuff if you have to.