For a custom PHP CRM using PostgreSQL CRM with Docker, look for a cloud VPS plan offering full root access (needed for Docker) and flexible resource scaling (so you can bump CPU/RAM as your CRM grows without migrating servers).
Minimum starting point: 2-4 vCPU, 4-8GB RAM, SSD/NVMe storage; PostgreSQL benefits from decent RAM for caching. Make sure whichever provider you pick supports KVM-based VPS (not OpenVZ), since Docker needs full virtualization to work properly.