Flying with a toddler (15 month old)

Our family recently has been offered a really great deal to go on vacation and basically have accommodations paid for, all we have to cover is flights. We also got married in December and haven’t gone on a honeymoon so we definitely want to take advantage of the opportunity but I’m super nervous about flying with a toddler. I also am struggling between buying her a seat or just keeping her in my lap. She definitely will ask to be held and probably nursed for a good part of the flight, she’s not a huge fan of the car seat so I think we possibly could save money on tickets if we decide not to buy her a seat that she won’t sit in for the majority of the flight but also it would be nice to have the extra room? Regardless, I’m stressed about flying with her just because of the stigma behind babies and kids on planes and I feel like people aren’t very understanding about children crying and fussing during travel. Does anyone have any tips for making it easier for everyone?? Thanks in advance