When buying clothes focus on buying clothes that fill out your wardrobe as a whole, not clothes that fit specifically into an outfit. The clothes in your wardrobe should be versatile and interchangeable. The ties should be able to be worn with all your suits. The shirts should go with all of the ties. The suits should go with the shirts and so on. While one set of tie and shirt and suit may look great together, you can certainly switch it up as needed.
Buying only outfits makes your clothes repetitive and predictable. When you wear the tweed jacket with the purple tie and white striped shirt every time, people will no longer think it is an interesting combination, and instead find your wardrobe boring and downright unoriginal.
If you think of the wardrobe as a whole, with holes that need to be filled, then you will have more universal and interesting wardrobe. The clothes become puzzle pieces and fit together beautifully. The same shirt and jacket will work with every tie in closet. The gray suit works with every shirt in the wardrobe. The red silk knit tie will fill in that gap in the wardrobe you have been thinking about.
This is way we stick to gray, blue and brown suits, in general, as they are more versatile and useful. And avoid black suits as they are limiting and eventually useless. We avoid suits with pinstripes in colors like pink and purple and green, since they limit the options on shirts and ties that we can wear with them.
Only as we fill the holes of our wardrobe do we add the unusual pieces and colors. Having a dark gray suit, navy suit, tan suit, medium gray, light gray and brown suit do we expand to the pinstripes, glenn check, window pane and hounds-tooth suits. This will ensure that our wardrobe is never boring, provides us with true longevity and the clothes will fit all occasions.
Of course, their are exceptions to the rules but keeping versatility in mind will keep your wardrobe fresh and interesting for you and others.