Hi. I love in MK and grew up around here so know it well. There are lots of lovely places - mainly outside of the central areas - and like anywhere, you’ll pay more for somewhere with “little deprivation” and good schools.
As a general rule, have a look on a map - if the grid square has mainly straight parallel roads within it, avoid. This is the info I was given by someone involved in town planning! His words “sounds a bit fascist, but it’s true”. Areas such as Fishermead, Oldbrook, Beanhill are part of the original plan and have aged badly. Of course there will still be nicer houses within them, but as an area generally, especially as there’s so many nicer new areas to choose from, I’d avoid.
The main problem you’ll have is that MK is designed for cars - the whole ‘city’ is based on the grid road system which makes driving everywhere quick and easy, but bus services are not known to be amazing here. Most bus journeys mean having to travel into the city centre to swap onto a different bus and then go back out again. A 5 minute car ride can be a 1 hour bus journey.
So I’d suggest finding out where you want to live and then checking out bus routes just in case (although to be fair, a taxi from the shopping centre to the outer grid squares would be less than £10 so it may be cheaper to do that than to drive anyway, once you take into account parking, fuel, insurance etc! )
If you want somewhere older with a bit of character, then MK village, Loughton, Woughton on the Green etc are very pretty, but prices would put me off a little there, especially if you end up having to travel for school. I’m in Middleton, which has some of the best schools and is quite expensive, but just a general 1990s build type of estate, nothing special. (Was lucky to get a good deal on our house!) If I had to move anywhere else I’d look at Newport Pagnell, a small town of its own now within the MK boundary, Furzton (pretty lake) or Brooklands - nice parklands - I think.
A more self contained area like Stony Stratford, Newport Pagnell or one of the nicer parts of Bletchley might suit you better, as you’d have easy access to MK but also have your own shops and banks, takeaways and pubs etc on your doorstep.
Most grid squares have a small shop (Tesco express or Budgens etc) which you could walk to, but for a bit more choice and interest, one of the places above would be better for you if you don’t drive. HTH