Ryanair, definitely no frills, of any kind lol
Take hand luggage as opposed to a hold bag if you can. They charge an admin fee for booking with a card though, even a debit card!
I booked a Ryanair flight for hubby recently, it was 2€ one way and with the add-ons the final total was 15€, so still a bargain.
Booking early usually means a cheaper ticket price too
I prefer Easyjet but they don't fly to where we need to get to so we end up with Ryanair.