Buy for well-solved, common workflows — reporting, content drafting, basic automation — where mature tools already exist and building from scratch just recreates something already available. Build, or at least customize, when a workflow is specific to your business logic, like a proprietary lead-scoring model or a unique data blend that no off-the-shelf tool handles well.
Most lean GCC marketing teams overbuild early and end up maintaining fragile custom tooling nobody can fix once the builder leaves. A safer default is buying for the first 80 percent of a workflow and reserving custom build for the specific gap that actually matters to the business.