Gas sensing techniques allow for groundbreaking studies in the field of plant-physiological processes, soil-bacteria interactions, as well as early stage monitoring of disease states via human breath analysis. Easy-to-operate, miniaturized, on-site, and cost-efficient gas sensors have attracted great interest in the scientific community in the last years. In this work an innovative fiber-enhanced Raman multi-gas sensor was designed, developed, and tested for manifold applications in the field of clinical diagnosis and environmental science. By combining the versatile Raman spectroscopic technique with state-of-the-art low loss microstructured optical fibers (e.g. HC-PCF), which show very low sample demand, a tremendous signal enhancement was achieved for potential monitoring of a complex volatile anesthetics matrix, or for the diagnosis of metabolic diseases including lactose intolerance, fructose malabsorption, or SIBO. The versatility of the new sensor allows simultaneous identification and quantitative monitoring of various climate-relevant gases and volatiles, especially of stable isotope tracers (e.g. 13C, 15N) and homonuclear molecules (e.g. H2, O2, N2) in a high dynamic concentration range and high chemical selectivity, without cross-sensitivity and the need for sample preparation. Furthermore, the application of a miniaturized, cavity-based Raman multi-gas sensor was applied for profound insights into plant functioning such as the link of more drought-tolerant pine to its greater flexibility in substrate switch for plant respiration under drought and shading. Future investigations on device miniaturization, cost reduction, low maintenance costs, easy operability and calibration, together with low power consumption will enable these Raman instruments further to be used for the elucidation of complex environmental processes and easy-to-apply, point-of-care diagnosis of metabolic disorders and diseases. Thus, it can fill the gap of already well-established analytical techniques.