I'd say your primary focus should always be to develop a few domains into good websites and park the surplus. I registered many domains before but only a few get hits and make a few cents only. In order to make a decent sum, you need either:
a) a few good domains
b) many, many "lousy" domains
But one good website making $x,xxx or more a month is the ultimate goal which is possible...and you move on from there.