Is your house still feeling cluttered?
When you look around, does it look like there's too much stuff?
I think a key is to have clear surfaces, and a clear floor. If you don't use it, to part with it. For example, in the kitchen, ensure all the surfaces are clear of clutter, have as much put away as possible.
Is your entryway tidy and uncluttered? Having a place for everything is essential, too - so when the DCs have finished playing, they know where to put their toys. When they finish their homework, put it straight in their school bags, rather than leaving it on the table. Do you all follow the 'one touch rule'? It has transformed my life!
It is much easier to clean & keep everything tidy once you have decluttered, but then having reached that point, there are methods to help you keep an organised house too.
It might be that you have already done enough, it's hard to tell without pictures. Good luck with the sale.