I've already given lots of baby gear away... what will we actually need to purchase?

Unexpectedly expecting our 2nd baby, there will be a 17 month age gap. We live city-adjacent in a town house with a small SUV and not much storage space, so I'm trying to figure out what we will actually need. I've already gotten rid of a lot of baby gear already, and will probably have to repurchase a lot of basics. My big questions off the bat are:

• How awful would it be to not get a double stroller? If a double isn't needed, how do you manage? Baby wearing one? Tush baby? Make the older one walk?

• How bad of an idea is it for the babes to share a room (around 20mo & 3mo)? We'll likely have the baby in our room with us for the first few months, but then what?

• Diaper bag tips for two? One big diaper bag with separate compartments? Two bags?

• We have no family or support system near by, recommendations for handling the birth?

• Would it be tacky to announce/gender reveal at eldest's first birthday? I'll be 18 weeks.

Any other tips/tricks/recommendations of things to do before baby arrives would be deeply appreciated. I feel like I was just starting to get the hang of being a mom, and now I'm back into flailing mode.