Office manager at a 90-person games studio in Wellington, now also the pay person

I am the office manager at a games studio in Wellington with about 90 staff. Over five years my job has grown to include onboarding, contracts and now, as of last month, pay. The two founders have always decided salaries themselves and have asked me to bring some order to it before we hire another 30 people.

I have no HR qualification and no background in reward. I found this community through a search for how to build salary bands.

I am reading back through older threads in this space, which are already helping. I will have questions soon, probably starting with how many levels a studio our size needs.