Transforming on the X and Y axis can be confusing, but it doesn’t have to be. For example, say you wanted to scale to the right of the object, but didn’t know which axis would allow you to scale in that direction. Instead of looking around in the viewport or trying to study the axis display in the top right, you could use the middle mouse button.
For instance, if you wanted to scale to the right, exclusively on one axis, you would press “S” key, hold the middle mouse button, and drag in the wanted direction. As soon as you have the right direction selected you can let go of the middle mouse button and continue to get the scaling exactly right. This even works with scaling on two axis exclusively. All you have to do is press “S” key, hold the middle mouse button, and drag in the direction of the axis that you do not want to scale on. After this is done, you can continue to scale on the two axis.
This method can also be used for the Move and Rotate operators as well.
Granted, selecting the right axis to scale on in a 3D space can be hard at times, but this method of selecting an axis to scale on is a real time (and sanity) saver.
Hope this helped!