The European Union's initiative on European data spaces aims to support innovation and economic growth by facilitating secure, interoperable data sharing across key sectors such as health, energy, and mobility. Within European data spaces, high priority is given to adherence to FAIR data principles. Thus, data and services should be findable, accessible, interoperable, and reusable. Ontologies as semantic models are fundamental in achieving semantic interoperability, as they provide a common framework for data and service access, discovery, understanding and reuse. However, the inherent complexity of data space initiatives, coupled with their underlying domains diversity are key challenge facing optimal FAIRness. This motivates the need for an agile methodology that aligns with data space principles, integrates existing domain standards, consolidates the use of metadata for ontology's FAIRness, and engages various involved actors (domain experts, data service providers, ontology engineers) towards the development of common data space ontology. In the frame of the OMEGA-X project, aiming to build an energy data space, this paper presents AIME, an ontology development methodology integrating the reuse of both standards and reference ontologies to enable the development of modular ontologies for data spaces. It leverages agile principles to strengthen communication between various stakeholders through different steps: reference standards and ontologies selection, selection of use cases, design and selection of interaction models capturing data exchanges, ontology modules creation, automation and continuous integration features to support the entire original ontology engineering phaseand reuse by data space users.