How Can I Implement a Fair Salary Grade System for Our Growing Team?

Seniors,

I need your guidance on how to create grades in my organization. We have an existing staff strength of about 35 employees and have huge expansion plans for this year. As of today, salaries are decided arbitrarily, and I foresee a huge problem. I want to create a grade system as soon as I join the organization - please help me.

Please see the attachment, but this is a general guideline. You may have some other slabs for your organization.