personally i couldn't justify buying expensive nappies when i knew they'd be grown out of so quickly.
i used folded muslins in the early days, and these were brilliant as they dried so quickly i didn't need hundreds of them, and they are still being used now for normal muslin use, so it feels like great value for money.
small little lamb bamboo was good - not too fat between the legs which is great for littlies.
small itti's i had a love/hate relationship with, when they worked they worked brilliantly but then i'd have a week of them leaking everywhere. they were her first night nappy and did a great job at that.
also liked bg's from a couple of weeks old - with a thin insert they weren't too bulky and did the job.
perhaps it also depends how big you expect your liitle one to be. i epected big, and she came out over 9lbs so i doubt any of the xs's would have fit her anyway.