There are three buildings that can be researched. When it becomes too expensive to research something, switch to a less important item. All research will be useful.

Command Center: Although not particularly useful, you can consider Preparation, Home Game and Nurse first then upgrade everything else when you have free resources, workers or time.
Laboratory: Concentrate on research that helps your boats and keeps them alive such as their health and shields.
Town Hall: Concentrate on things that help around your base that always give a benefit. Select the ones that give you more resources or save resources first. The Promotion or Respect the Boss are not that useful.