The formatting/partitioning of the drive really depends on what you'll be doing with it. If this drive will be Wii dedicated, then it's recommended you use FAT32 with a cluster size of 32kb. This way here you can USB load GC games too if you want to/your Wii is capable of using GC controllers.
If you don't plan on using GC games NTFS is the next best choice as it's also completely readable by windows. This way you can still manage your HDDs contents on your PC.
WBFS is no longer recommended because, among other reasons I've read about, once you format to WBFS the ONLY thing the drive can be used for is Wii games.
As for which drive to get, we have a HDD compatibility list here: