Looking for advice for an isometric aiming system and soft grid system

Hi, I'm a bit of a novice to Unity and I am trying to make a quick action game from an isometric perspective.

I am currently trying to work on the abilities where the user may simply press Q or E then left click a space on the ground to send an attack out in that direction within a certain range.

The basic mock up that I am trying to get working is simply having a GameObject with an invisible child GameObject that acts as a spawn point where if the user clicks it will spawn a single prefab cube which will then travel down the ray originating from the spawn point.

I have been looking into trying to get this working with raycasting but most of the examples I have seen are for first person shooters. For a better example of the effect I am trying to achieve think the combat system in Bastion or Transistor or spell casting in MOBAs.

The other question that I was wondering if anyone could shed some light on establishing a soft grid system? Essentially to assist with possibly simplifying enemy movements and ability effects I planned to establish a grid system that the character could move freely on but attacks and their current position would be dictated by which space on the grid they occupy the most. I figured this would be a way to better manage how attacks are calculated and managing simple enemy ai. Would this be the right way to go about things?

Thank you for any help that could be provided.