Hello Jane,
In inter-organizational trust research, tangible investments like training, product specialization, special systems, special pos displays, etc. have consistently been shown to build trust because they signal a long-term commitment and an investment in the other (i.e., a sign of benevolence). This can apply within an organization too so beyond being credible, fair, signalling benevolent intentions (so important), investing in others pays off when it comes to trust.