Frontier Airlines has $14.99 one way fares for Las Vegas to Newark EWR on limited dates from Nov 14 to Feb 12. You can actually book a $14.99 all-in one way ticket if you travel with only a personal item and wait until check-in to be given a free seat.
There are several other cities with $15 fares to Newark, including Atlanta, Miami, Orlando, Phoenix and West Palm Beach.
Las Vegas to Newark pre-selected seat at booking is a minimum $21, add one checked bag for $34, add one carry on bag for $37.
A package bundle for an additional $68 provides pre-select seat, checked bag and carry-on bag for a total $83 one way LAS-EWR ticket price.
Frontier Airlines Las Vegas LAS – Newark EWR
$14.99 Tue Nov 19
Frontier Bundled package choices
Or just fly cheap with a small bag that fits under any seat the airline gives you.
I traveled to Denver a couple years ago in late October with my 30L backpack as my under seat free personal bag. I even traveled to Iceland in early April 2017 on WOW Airlines for a 10-day Europe trip around Reykjavik, Lithuania and Latvia with only my free personal bag backpack under the seat. Although, I definitely prefer to have a full size carry-on bag too.