Our experience as first-time parents was: it's a bad idea to buy a lot of stuff up-front at all, and when you do buy, it's probably best to always buy the moderately-priced version first and only upgrade if you discover you have to.
The issue is that parents and kids are different. Some things that other parents say their child loved, our child would have nothing to do with. (And vice versa.)
For example our son has never had the remotest interest in a pacifier, so we have some of those still in shrink wrap. Or for baby blankets, only a certain kind (thin cotton muslin) would hold him in a swaddle, and the other kinds were worthless. We went through a couple different sling/carrier contraptions that he wouldn't tolerate. Various kinds of bottle. Co-sleeper. On and on.
Buying anything baby-related is hit-or-miss because it depends so much on your specific child. Other people's experiences only go so far.
Making it worse, it's tough to even predict your own habits and what will work for you post-baby. Some cherished routines today are probably going to change.
Strollers are no exception. We got a moderately-priced one, and we just don't use it that much, so it's held up well. But we didn't know in advance that we wouldn't use it that much. We also didn't know that our child would be happy to sit in it, though he is, thankfully. But I'm sure if we'd bought the super-expensive stroller, we'd have the child who hates strollers with a passion. ;-) It's just inevitable!
Another stroller-specific point, I don't think one needs a stroller for a newborn. Newborns are not very heavy, and you can just carry them, or carry their car seat, or get one of the many solutions for strapping them to yourself. A stroller is more for at least a few months down the road. Our experience anyway. So it's easy to buy the stroller later.
I'm pretty sure that if you get the moderately-priced version of everything (and buy everything "on demand" and as late as possible), you'll save enough money that you can re-buy the most expensive version of the one thing it turns out you should have splurged on. If that's the stroller, so be it.
If you're missing something, you can (and will) run to the store and pick it up. If it's not an emergency, the Internet is happy to deliver any product to your door in two days. No need to "be prepared" beyond the barest basics.