Bands are honestly personal choice. And ANY band which keeps the watch firmly enough to your wrist will do what any other band which keeps the watch firmly enough to your wrist for the sensors to work. You don't want the band too tight. You don't want the band too lose.
As to materials, you should decide what you'd enjoy wearing the most. You can choose silicone, leather, metal, etc., and not one is necessarily better than another.
I have amassed a large Apple Watch band collection over the years and I change my band often, to suit my attire or the environment I'll be in in a particular day. Do you need something to swim in? Go with Silicone. Do you want something more elegant, go with leather and/or metal.
You might want to stop by your closest Apple Store, where they have displays you can see and try on the options Apple sells to get a sense of you think might work best for you. And once purchased, you are not limited to only Apple band options as there are thousands of aftermarket options out there, some of which are very high quality.