My toddler is not usually one to dress up, as his typical outfit is gym shorts, a stained shirt and crocs. However this doesn’t necessarily work for formal settings. I went on amazon and found this cute little romper styled as a suit. It’s one piece, light weight, and is made out of a super soft material. A very bang for your buck outfit too, as it was available for only $20. 
However there are its downsides. It does not wash well as when it came out of the wash it was covered in wrinkles. We thought we bought black but it was more gray when it arrived, so be cautious when ordering. However my biggest problem was that the legs were not long enough, giving it a cropped pant kind of look. While this isn’t terrible, it’s not necessarily something we were going for. All in all I recommend this piece for anyone looking for a more formal, cute outfit for their toddler.