Now you have found a suit that suits you, you probably need to get a shirt too. Now of course a suit can look nice with a jumper. Some men suit a polo or turtle neck with a suit, but it can be a difficult look, even if you are James Bond.
And a T-shirt is worse, on the whole. But the worst thing is a jumper or T-shirt that shows the chest – especially chest hair.
My rule would be if you want to wear a suit, also wear a shirt. If you must wear a jersey or T-shirt pair it with jeans, casual trousers or shorts. If you are very, very cool you may be able to break the rules, but then if you are very, very cool you don’t need advice.
The rules for shirts are related to the rules for suits. Buy for your body shape.
If you are angular (chest is 7″ or more greater than waist, and shoulders are wider than hips), you should wear a tailored shape, so that you don’t have loads of fabric around the middle. You can tuck the shirt in and it looks neat. If you are slim the slim fit shirt will probably work well. Choose smooth, crisp fabrics.
If you have a straight figure (appears straight with less than 6″ difference between chest and waist), you should choose a straight cut shirt, in medium weave fabric. Most styles of shirt will suit you but avoid a very tailored look.
If you have contoured (softer outline, bulkier, often stocky) shape, then choose a “classic fit” shirt. This is a more traditional shirt shape and often cut a bit looser making it more comfortable. Avoid crisp fabric and the slim fit cut. Softer cottons and other fabrics will work well (unless you are overweight – see below).
In terms of collar types I would say that the traditional formal collar is good for all business wear.
The cut away collar is designed to look best on men with very long faces – otherwise avoid it. I think it looks odd on a man, and would be interested in other views. It seems to be paired with contrasting collar and cuffs, another look I personally dislike.
It seems to be chosen by “trendy” men, but to me it looks like the collar is too small. What do you think?
The button down is a casual shirt and can look very nice, but not for the most formal occasions. In terms of fit you should be able to get one finger comfortably between your collar and your neck. I prefer the double cuff, with tasteful cufflinks, but of course a nice button cuff is just fine too. Just avoid the short-sleeved shirt for work. My post on what not to wear for work may help.
If you are overweight chose a stiffer fabric to provide more structure. Make sure the neck fits well so it does not look like the shirt is strangling you. Choose a longer/more pointed collar. Make sure there is enough fabric in the shirt so there is no gape.
If you are a smaller man then make sure the collar and overall look of the shirt is smaller scale, and probably avoid a patterned shirt. It is really important to get the sleeves the right length.