As New World Empires captures 400 years of human technology and advancements, you will not be able to recruit any type of unit or construct any kind of building right from the start of a game round. Instead you will have to research most of them first. Open the Research panel in the top left of the main screen to get an overview about the available researches in each of the three different branches: Warfare, Economy, and Colonization.
The Research Panel
One of the unique aspects of New World Empires is the fact that researches are tied to Eras, which in turn only become available once a certain number of real-life days have passed. Era II level researches will become available after 5 days, Era III level researches after 10 days, etc. Click on the Era icons to check which researches become available at which point in time.
Researches unlock new types of units and buildings, improve the abilities and effects of existing ones, or grant other benefits. However, researches come with a certain research time and research costs and are dependent on other researches. Some examples:
All researches from Era II or higher require that you first complete the respective Era research (selectable on the top right of the screen).
All unit and building researches Lvl 2 or higher require all prior research levels of that unit or building.
Some unit researches require other unit researches to become available (e.g., Light Regular Cavalry requires that you research Light Regular Infantry first).
Many unit researches require other building researches to become available (e.g., Mercenary Infantry requires that you research the Mercenary Camp first).
These dependencies will force you to focus on one or two of the available research trees. If you are looking for military dominance, you should invest in the Warfare research tree. If you want to support your military endeavors with a strong economy, check out the researches in the Economy tree. If you want to claim the riches found in overseas territory, make sure to invest in the Colonization tree.