This is a particular (albeit popular) way to think about clothing, but it's not necessarily the proper way. If you do as 12345Michael54321 instructed, be cognizant that the "eye" you're "developing" is one upheld to be good by a particular group of people – a group that pays particular attention to clothing but certainly not the majority of the population or final arbiters of good taste (whatever the term may mean). You're not going to be disqualified in the same sense as you would be if you wore an improper uniform to a BJJ match.
Originally Posted by 12345Michael54321
Look at pictures/videos of men who are generally deemed to dress well and who typically wear traditional/classic looking suits. Study how these men look in their suits.
Eventually, you will develop an eye for properly fitting traditional/classic suits.
The worst that happens is that a particular group of people are going to think that you have bad taste. (Though another group may think you super stylish – god knows the people who go around "deeming" people to be "well-dressed" (e.g. the people who populate the references E,TF suggested) are not universally admired for their dress.) I doubt that what people think of you is your sole or, perhaps, primary criterion anyways.