Exchange your currency at Legian Street, everywhere else in the Island will be lower rate
Carry water bottle and fill it when you find water dispenser, you will save tons of money
Eat at Warungs, same food in a restaurant will be double the price
Take your own medicines and bandaids and first aid kit, doctors are extremely expensive
There is no public transport and taxis are expensive, so either use a bike or take shuttle buses
Seminyak has upscale hotels and resorts but the party scene here is nice on the beach shacks....