Which level of the company (casual workers, mid-level, managerial or executive management) needs most attention in terms of resources and funding?

Thanks 

In my opinion managerial and executive level, since focusing on management lead to high performance on mid and ex- level, so you need to develop high level and develop it first. 

My experience has shown that the mid-level Officers in the organisation have the most impactful input for the organisation because they bridge the vital gap between the executives and the lower level workforce.