On a plane with a puppy Oregon to NY – looking for travel tips please

I'm picking up my puppy in a couple weeks. We have three flight legs. All things working perfectly we fly out at 5 am for 2.5 hours – 1-hour layover, 3.5-hour flight – 2-hour layover 1.5 hour flight and home

She's tiny. Will easily fit in a carry-on "crate" under the seat.

What should I bring? I mean, she's a baby so chew toys will be kind of big for her and so new to her as to be useless. I probably want to with hold food? Save water for layovers.

Anything I can do to make the experience as peaceful as possible?

According to the airline there's an extra charge? $150. When do I do that? I need to call the airline tomorrow haha.

I've read many many posts but most of them are years old.

Any tips would be appreciated. Thank you!