Well, you could set some low morphological costs for realism, then set the cost multiplier to 0, then turn Dynamic Costs on. Set the target population to a level where your sim runs at a decent speed, then an upper and lower percentage to try and keep the numbers of bots within the target.
I think the first priority is to have bots that reproduce regularly before they do anything else. Use ageing cost to encourage that.
In my personal experience zerobots are just hopeless to get anything from nomatter if you have costs or not, so I've gone over to randombots instead.
Right now I have a stable population of randombots on my laptop. Sometimes they peak in population, but the faster they peak, the faster they drop too.
I think the best results are when the population graph looks like a small sawtooth pattern instead of peaks, drops or flatlines.