I was looking to get into this just the other day, did a bit of research, resin seems a lot easier to do if you're a beginner and the materials are more easily availible, you can even get away without using moulds for somethings. I have been put off though, having made a few moulds in the past for aluminium, I found it to be a lot of work, it takes a while espically with very small parts to get the runners and risers right.
I haven't used latex moulding techniques,but if you have the part you want replicate and it is fairly simple they seem a very quick way of casting. With white metal, I think there are cetain types, some for bog standard casting (which must contain lead) and some for centrifugal (which don't have to), be prepared to put up with a few fumes!