Layout/theme/site organization

I’m hoping someone can get me aimed in the right direction. Despite reading an eBook about WordPress I’m not sure how to set up the organization of my site. I know basically what I want, just not sure how to accomplish it with this software.

This may be largely a theme issue or something else. Quite honestly I have trouble telling one theme from another and not sure what features I need.

My site is a betta breeding blog and sales. I basically want a separate page for each of my spawns, currently about 10 of them. So I can make posts as the bettas grow up with a lot of photos and videos. I don’t know how to setup these 10 different blogs on my one site and keep all the posts for the separate spawns separate. I will also have a separate page for selling bettas, either directly on my site or just links to a 3rd party auction site (ebay or aquabid). My site is friedbettas.com if someone wants to look, but there isn’t much there yet. I’m not doing anything else fancy with the site just need this layout and obviously the navigation to get around the various pages.