It is surprising to note that you are the first HR manager in a company that already has 225 employees. They must have had an HR department and processes already. How did they manage until now?
Setting Up HR Operations
When setting up HR operations, you need to start with those that are already problematic, then move to potential issues, and finally to other areas that need streamlining or implementation. Generally, attendance and payroll will need to be taken care of. Without knowing the details of your current setup, it's difficult to say what you need to do.
Geographically Dispersed Model
But remember that you are moving to a geographically dispersed model. Therefore, new methods must be established for accurately recording attendance and validation. You will need to ensure there is a foolproof way to record attendance correctly or have someone trustworthy at the remote location to report any deviations and false attendance.
Leave Rules and Records
Leave rules and records are the second important consideration. After payroll, you need to establish job descriptions and the organizational structure (reporting patterns, responsibility matrix, etc.). Following that, proper employee records/files as well as appraisal methods need to be addressed.
Grievance Redressal Mechanism
A related task would be setting up a grievance redressal mechanism, including mandatory forums such as those for reporting sexual harassment and whistleblower policies.
HR processes, employee manuals, and related matters are next in line. There may be other tasks that you will need to add at various points in the process above.
Regards