This can be the most frustrating map of all game thanks to the tiny areas. It's necessary to save and load to check whether a new room fit your design.
One strategy is to avoid using the central L area which is basically only good for corridor.
With that central idea to keep in mind, you can build up the initial area as GP and diagnosis but gradually pushing the Ward and pharmacy to area north. Later on the Ward and Optheatre can be moved to area to the right of that, leaving space for 3 more small treatment rooms.
West of GP area can be start as a R&D training space, but later on move them up north of that, leaving space for more treatment rooms. You can buy more areas for spare space for spare rooms later on, just as long as you keep the L area unbought and the headaches will reduce immensely. Happy Hospitaling!