If this is your first time doing this, likely best for to first hire a full time or Fractional CTO to hire this team.

There are just to many variables to consider.

The primary variable is the code you're producing + how to ensure quality.

A CTO, with decades of experience + well versed in all manner of technologies, is essential to ensure you're correctly allocating developer funds.

If you miss this step, likely you'll either overpay or underpay, almost surely having problems delivering product + ensuring delivered product quality.