The word "tacky" doesn't really mean cheap. You can have a very expensive "tacky" suit. To my English ears the word describes something that is out of style and in bad taste. So you can definitely use it to describe your taste in dressing style, but you can also use it to describe your taste in behavior. Some people may disagree with me but I don't think it's a very insulting word when you're describing objects because everyone knows that people have different tastes in cloths, cars, etc.. But it CAN be insulting if you describe a person as tacky.
"MY gosh, you shouldn't eat steak by HAND. YOU'RE really tacky." - You could say this, but it's a little rude to say YOU'RE really tacky. It's better to say THAT'S really tacky, because then you're describing the action as tacky and not the person as tacky.
"Damn, I don't like your look today, it's really tacky." - Perfect!
Example of tacky style...
-Wearing a belt and suspenders at the same time.
Example of tacky object...
-Having a toilet made out of gold.
Example of tacky comment...
-"I'm lost. Can you give me directions to your heart?" (Note: if this comment really made you cringe then it can also be described as "cheesy" as well as "tacky")