Definitely a good idea to do many batches to start with. They always turn out great, or at least drinkable. I started with only one batch and ran out of beer as my second one was almost done.
As for the twang, try to get the freshest stuff you can. So go to a large home brew store that sells a lot. And only add 1/4 or so of the extract in the beginning of the boil and add the rest at the end. Late extract addition is what it's called, and it helps keep LME from being caramelized.