What kind of tank? What fish do you think you want? It is good to try and figure that all out first, as the order you add them will be based on how aggressive they are. Check out places like liveaquaria.com or Bluezooaquatics for ideas and be sure to pay attention to the suggested tank sizes. Liveaquaria tends to go bigger than most other sites, but I also tend to agree with their suggestions, as other sites often go too small.