Every dance tells a story. The right clothing makes this story more immersive.

The fanciest clothes are white tie and black tie. This is bad for dancing because the shoulders on tuxedo jackets look bad when you lift up your arm. Practicality always trumps fanciness so white tie and black tie should not be worn social dancing.
A tuxedo jacket should never be removed in public, so if you end up in a ballroom while wearing a tuxedo then you should keep the tuxedo jacket on while dancing. Unless you get too hot in which case practicality trumps custom.
In other words, here are the Three Laws of Dressing Nicely:
- A lady/gentleman shall dress practically, as dictated by circumstance.
- A lady/gentleman shall dress according to custom, provided such clothing does not conflict with the First Law.
- A lady/gentleman shall dress nicely, provided such clothes does not conflict with the First or Second Laws.
A waistcoat is is the best clothing centerpiece for a lead to wear social dancing because it’s the fanciest top that allows a man to lift his arms. A waistcoat should be worn on top of slacks, a nice shirt and (ideally) polished shoes. You can find a each of these at Goodwill for around $10. A shoe polishing kit costs another $10.
If you can’t afford all of this kit at once then start in reverse order. Buy nice shoes first, then a nice shirt, then slacks, shoe polish and finally a waistcoat. It’s worth searching a long time for the right waistcoat. A properly fitted waistcoat makes you look young, spry and well-off. You can wear it to social dances at any level of formality.
Though a waistcoat is the eye-catching bit of clothing the most important bit is your shoes. Get a nice set of leather dress shoes. They can be brawn, black or even red. They can be oxfords or derbys. Here’s a chance to show off your personality. If you want to dazzle follows, polish your shoes. Don’t worry about getting specialized dance shoes. We’re not doing ballet here. If it’s comfortable to walk in you’ll be fine.
You have lot of freedom in what kind of dress shirt and slacks to wear too. Just make sure nothing clashes and your total outfit isn’t too cluttered. No more than one article of clothing should draw attention. Everything else should be subdued.
It’s socially acceptable to go dancing with a t-shirt, sneakers and jeans, but you’ll have more fun with this outfit.