When to upgrade ship class? Hordes vs. speciality ships

I've been a fan of critical mass vs expensive units strategies, sending mass cannon fodder to clean up ships that take longer to create and use more resources against my GunBoats.

I have seen that there are strategies of using mixed fleets with Railguns and missiles and lasers to cover mixed weaknesses.

After many learning games where I end up overwhelmed, I am playing as The servants, to get my first victory.

I am clearing stations and enemy ships with my fleet of 10 Gunboats of 70 power each, in the year 2033.