Add structure when there is a reason
Departments and approvals are available from the Business plan. Introduce them when you have a real need, for example finance reviewing discounts or a regional team that should not see another team's records.
Start with departments
Mirror how work is actually divided, not the org chart in full. Keep names recognisable and ownership obvious.
Approve the exceptions, not the routine
An approval step is worth its delay only when the decision carries risk. Pick two or three triggers, such as a discount above a threshold or a non-standard contract term, and leave everything else to normal flow.
More control for larger organisations
Enterprise adds custom field rules, multi-level approvals, SAML and SCIM, and a 7-year audit log for organisations with governance requirements. See enterprise controls and security for the detail.