Most forms of construction offers faster completion, cheaper costs, or a completion bonus. Due to this, you should have sufficient resources to produce additional units and buildings within a given time.
Generally, building your air force is highly recommended as airbases will automatically contain two free fighters (as long as your population limit is not full!) and air units are created faster and/or cheaper.
Meanwhile, having a strong navy wouldn't hurt as submarines and fireships are produced cheaper and faster.