The number one rule is don't dress like your Rich,As much as you want to be stylish...your making yourself a target to be mugged or robbed.....any type of Luxury brand watch,Armani clothing will make you stand out..I've always heard this from locals and veteran travelers...There really is some people who think its okay to wear a gold watch worth value in poor places.
other then that,Bali is such a cheap place...1.50 breakfasts...and 100 dollar a night private hotels with your own pool...like in this video below