Hi! Simple question but I know it is a complex answer.
If I am starting a brand new main account from scratch for my brand, what are the minimum standards (# of Followers, # of Photos, engagement, etc) the main account needs to have before you create a slave network around it? And, what do you do to expedite those standards (Buying followers, buying automated engagement, etc…)?
Assume account has zero followers, zero posts, and just a fully working ecommsite linked.
You need at least 15 posts and a few hundred followers. These followers need to be real and targeted otherwise your page will have bad engagement from the start.
Ie. Our slaves start on 300+ follows and have 15 posts minimum so they will already look better then a new mother account if its not setup well.
Do you mean your slaves have 300+? Or the main account has 300+?
And how do you get to 300 are you doing like Manuel Follow and Follow?
Before starting a “new network” of Mother/Child like you said, what’s most important is the content. You need quality content especially if you have low posts number - 12 to 15 posts (Reels, Pictures,…) are needed minimum, and 30+ would be way better. But that’s not only the only thing ; bio, story highlights and overall account aethetic should be on point.
Other than that, you don’t need to have followers before creating your own network. You can use it to grow your page, even from scratch - and the learning curve for M/C is quite big, so the sooner you start, the better 
Engagement isn’t necessary neither before starting a network, as the promotion will keep going as long as you maintain your network, and thus the engagement will kick in with it.
However, you mention running an ecom brand. So yes, you can start creating your network now, but it doesn’t mean it will be optimized at all.
If we are talking about funnel optimization and brand awareness/identity, a brand new account with “NEW” tag + no followers + no engagement, will most likely not sell at all. Step I would recommend :
Create your network ASAP and try R&D maintaining a healthy setup of child accounts. Learn from it.
During that time, stack up 10k fake followers, boost engagement in an artificial way (but realistic looking), so that your ecom brand is ready to sell, with quality content (+++). This way, when the promotion will kick in, people will be interested to buy and you won’t need to wait 946 years to start selling once you’ll reach your 10k marks thanks to Mother/Child only.
That strategy is meant to optimize sales, not to be copy/paste for every use cases obviously…
Yeah the fake followers thing works well if its a throwaway brand but if they want to create a super engaging bran with superfans etc the fake followers will kill that and make that almost impossible.
However if its 100% sales, Then a 10-100k followers and put heaps of fake comments, likes on posts etc. Just make sure you know the downside to using fakes @dangonochain