Well this is big process - will try to detail out as below
1. You need to define the PMS Process, Eligibility of employees who will fall under the review cycle - what would be cut-off date, Followed by what framework are you considering - Weather you intend to go via OKR Route or Review Route in review Is it going to be 3-point rating scale, 5 point rating scale, 360 Degree feedback process, You need to document this
2. Most Important aspect is sensitising all the employee about this process & preparing review templates
3. You'll have to carry out a research what is the market standard appraisal %age for your industry & this needs to be done at-least for the past 3 years - this would help determine to decide a ballpark %age increment
4. You need to do Budgeting of current salary cost vs Incremental Salary cost (after considering the market data & what are you willing to give),
5. You have to Initiate the feedback process & parallel create data sets & give a budget to Manager's/HOD's for hike %age of their teams - as there would be promotions, corrections etc - It always best practice to divide the budget amongst the 3 Parameters i.e Merit Hike/Promotion/Correction - this would help in overall analysis.
6. Goes without saying that once the discussion are completed Managers have to share their recommendations with HR & HR has to further spend time & apply Bell -Curve (Rationalising of Ratings) - This can be optional for 50 member Org.
7. Further to this the there are operational aspects which more around communicating etc.
From an India perspective - You can try to introduce tax saving component's..
As I said Initiating Appraisal process is a very big activity, so happy to explain over the call if you need any help