Formal greetings  sentence 
Good morning.
Good afternoon.
Good evening.
Good to see you.
How do you do?
How are you doing?
How are you?
How is it going?
Pleased to meet you.
Nice to meet you.
it's a pleasure to meet you.
Informal greetings/slang  sentence 
Hello / Hi / Hey
Hiya!
Goodmorrow
Morning / Afternoon / Evening
Yo/Yoyo!
How're ya?
How're you?
Howdy
How's it going?
How're thing?
How is everything?
How's life?
Long time no see you.
Lovely to meet you/Lovely to see you
Are you Ok?
Alright, mate? / Alright?
What’s the craic?
What's new?
What's up?
Sup?
Ahoy! / Ello!
Respond sentence
I'm fine thank you, and you?
I'm good thanks, you?
I'm pretty good.
I'm Ok.
Not bad, thanks.
I'm very well.
I'm great!/i'm great, you?
Pretty good, thanks, you?
Yeah! Not bad.
Not a lot, you?
I'm well.
Goodbye sentence
Goodbye/Bye Bye/Bye.
Have a nice day.
It was a pleasure seeing you/talking to you.It was a pleasure speaking with you.
Take care.
See you/see you soon/see you latrer.
See you around.
See ya!
I’ve got to get going.
Gotta go.
Talk to you later.
Good seeing you! 
Bye for now.
Have a good one!
night/nighty night.
Drive safe.
Safe travels!
Have a safe trip/flight.
Laters.
I’m out!/ I’m outta here!
Take it easy!