well that is an interesting question. If you do the math it's alot.
if Ramos is able to summon a spider every turn for 6 turns. that is at least 6 spider models. it takes 3 spiders to build a swarm model. Now if you have the brass arachnid and he stokes Ramos every turn you could conceivably summon 6 more spiders. So you're looking at 12 spiders and half that in swarm models. it's a ton of minis if you do it that way.
As for the Electrical Creation you only need one as only one can be out at a time.
However you don't need all that many really. I run with 2 spider swarms and 6 spiders and find I have enough models usually. while the idea of getting a spider or 2 out every turn is appealing it doesn't really work out that way and I find there are other things I'd like Ramos to do than finding scrap counters and making spiders but that's just me.
I will probably wind up picking up another swarm and a set of 3 spiders just to cover myself if I need it, but that is some time down the road as my spiders don't seem to last long as I tend to blow them to pieces.
So my typical starting set up is as follows for a 25ss game.
Ramos (2 cache)
Brass Arachnid --2
Steamborg --10
Arachnid Swarm --9
Arachnid --3
It's pretty much summon, stoke, summon and swarm. Then scatter and KABLEWY!
Hope that helps.