Currency
The Republic of Ireland uses the euro. Northern Ireland, including Belfast, is the UK and uses pounds sterling, and euro is not generally accepted there, so a day trip north needs different money. When a card terminal offers to bill you in Canadian dollars, always decline and choose euro. That offer is dynamic currency conversion and the exchange rate baked into it is worse than your own bank's, every time.
Cards, cash and the Leap card
Contactless is accepted almost everywhere, down to small pubs and market stalls. The exception that catches people is Dublin Bus: euro coins only, dropped into the machine beside the driver, no notes and no change given. Get a TFI Leap card, which covers Dublin Bus, the Luas and the DART on one tap. The private airport coaches are separate commercial operators with their own ticketing, so check their own websites rather than assuming Leap works on them.
Tipping
Not obligatory and not expected the way it is at home. In a sit-down restaurant around ten to twelve and a half percent if the bill has no service charge, and check first, because larger tables often have it added already. In a pub where you order at the bar and carry your own drinks, you do not tip the bartender at all. Nobody will think less of you.
Power
Type G three-pin plugs, the same chunky British ones, on 230 volts at 50 hertz. Your Canadian plugs will not fit and neither will a two-pin European adapter, so bring a Type G adapter specifically. Phone and laptop chargers are dual voltage and fine, but a Canadian hair dryer or curling iron built for 120 volts will not survive being plugged in.
Tap water and language
Dublin tap water is treated to EU drinking-water standards and is safe to drink; carry a refillable bottle and use it. English is spoken by everyone. Irish is the first official language and appears on all public signage, so Sraid is street, Sli Amach is the way out on the Luas and DART, and Failte is welcome.
Safety and getting scammed
Canada's advice for Ireland is to take normal security precautions, and the realistic risk is opportunistic rather than violent: phone snatching and pickpocketing around O'Connell Street, the quays and Temple Bar, often by small groups working a distraction. Keep your phone off the outdoor pub table and your bag in front of you. Use ATMs attached to bank branches rather than standalone street machines. Licensed taxis carry a roof sign and a displayed driver ID card; if either is missing, walk on.