17 months between my dc.
The first 6 months will probably pass by in a blur. But it will be fine, honest.
Things that got me through:
A sling. Keeping baby in a sling meant I could still get on with stuff with dc1 that we did before the baby came along.
A box of "special" books. Once the baby was here, after a week or so, I left baby with his dad, just for 45mins/1 hour and took dc1 to a couple of charity/book shops and let him choose some books. These then got put in his "special box". This was the box that came out a lot at the beginning when the baby needed a BF. While I was feeding baby, dc1 would come over and cuddle up with one of his new books.
A double buggy. We did use the sling a lot but a double buggy was great for long day trips to the zoo etc. Meant baby could happily sleep in buggy and I could lift older one up to see animals/eat lunch together while baby slept.
Also great for getting them both to sleep in then being able to park yourself up in a coffee shop with a book for 30mins or so.
Lowering standards. As long as we had food in, clean dishes and clean clothes, most other things housework wise got neglected for a while.
Find a loose routine that works for you but don't stress if it goes tits up, as it may do that a lot in the beginning.
Get a slow cooker.
I could go on but i'll leave it there unless you have any specific questions.
I think tbh, this is a great age, for dc1 to get a sibling. Generally, too young for sibling jealously but by the time they are old enough to understand things more, they can't remember a time without their siblings.
Mine are 3yrs and nearly 2 years now and it gets easier every day. Now they both play together and keep each other amused, egg each other on keep out of mischief etc.
And fight like cat and dog but I won't tell you that yet 