I have the 2004 LX Sedan, and I would like to put some rims on it. Will it look ridiculous if i put 18's on it? (too high sort of thing) does anybody know the max offset I should go? or is it alright to have 40+, is the jump from 17" to 18" really worth it?

I am unable to answer these questions myself because I cannot find many examples of people with '04 civc lx sedans with AM wheels.

Im sorry if I sound like a noob, some answers would be appreciated.

 

When you go "plus one" from 17 to 18, you'll need to get tires with a lower aspect ratio. So, the tire and wheel should have the same outer diameter as a 17" wheel. It will not appear higher but the gap between the tire and the wheel well will appear to be larger, even though it is the same unless you car is already lowered.
18s on a Civic are a bit large and, in my opinion, good for show but not for everyday driving.