A bit long but here are my thoughts...
Mine have had the following uniform so far (currently y4 and Y6)...
nursery... jogging bottoms or pinafore, polo, sweatshirt, black pumps (for indoors only) - this was great - practical, cheap, quick to wash, dry & iron (only sweatshirts were logo'd and weren't too expensive)
primary - either logo'd polo or shirt and tie (can be elastic or proper tie), logo'd sweatshirt, trousers (boys and girls), skirt or pinafore (girls), and summer term, options of shorts (boys) and gingham dresses (girls)
As the logo'd polo is a mustard yellow, it is not exactly easy to source a cheap version. A polo shirt costs around £8.50 and a sweatshirt is £9.50... whereas I can buy 2 non-iron shirts from M&S for around £7 (and usually buy on offer of 3 packs for 2)... if I was to buy them in tesco or asda, it would be cheaper still but I generally find the quality difference is noticeable after a term of washing...
As a working Mum, I usually kit my kids out with 6 shirts and 3 sweatshirts so that I can hopefully make it through the entire week without having to iron more than once... yes they sometimes end up wearing yesterday's lunch to school as I haven't washed a sweatshirt - but tbh I don't care any more about that one so long as its not a concert or photo day
That means the polo option would cost around 3 - 4 times as much for each child (and my 2 are about the same size despite a 2.5 year age gap so no hand-me-downs )
On that basis, after buying some polos when my eldest was in reception, I have settled on shirt and tie, and I think they generally look smarter and have had no issues about ties, other than the kids preferring real ties to elasticated ones as they are more grown up
If I was designing a uniform for a school, I would probably say
Foundation - joggers/pinafore, polo, sweatshirt or fleece
KS1 - trousers /skirt/pinafore, shirt, sweatshirt or fleece (no tie)
KS2 - trousers/skirt/pinafore/shirt & tie, sweatshirt or fleece
KS3/4 - trousers, shirt & tie, blazer or sweatshirt/fleece
6th Form - smart business attire with moderate jewellery etc allowed - get them used to dressing for a work environment (nb does not have to be a suit!)
And choose sensible colours (eg white polo or shirt) - no logo's on polos so parents can buy cheaper options
I have to say as the kids get older, uniform is a good idea as non uniform days are now fraught with "I don't know what to wear" and the "playground fashion parade" as my DD is 9, and all I seem to hear is so-and so is wearing XXX - for non-uniform day.
And tbh, its better that uniform gets spoilt with glue and paint than their new stuff (which of course always has to be worn as soon as its out of the shop)
uniform serves many purposes, including setting a tone for discipline and standards - if it is adopted and enforced sensibly, then it works