I have always had this question; what should be the standard and more readable space that we should add when design applications. So would like to know the best sizes for the space
There is not a standard to be found here for the specific question, as it touches on the broader context of vertical rhythm in the design grid of the page.
The vertical rhythm is defining line heights and vertical spacing between the elements. It gives your page a harmonic feel with a nice grouping of elements, that ultimately increase scan-ability and readability.
You could use a core unit like eg. 6 px, and make sure all height values can be divided by that down the page.
Next you'll want to make sure that components are grouped visually in clear way. It should be clear that the label is grouped with an input field below, and not any input fields or other elements above. You achieve this by simply increasing the distance between the component based on your core unit.