My advice around creating a grey Jedi is to decide ahead of time how your character reacts in certain situations - and allow for change as you progress and develop. This is what I did with my Sorcerer, deciding what her motivations and temperment would be rather than trying to hit a certain number of good an evil responses. The main things to plan for ahead of time will be:
- Is your character usually merciful to their enemies?
- Is your character especially sympathetic to others' emotions?
- Does your character believe in sacrificing civilians' safety if it means a victory for the Republic?
- Is there something from your (head canon) past that will affect their choices? Some sort of taboo (i.e. something that will affect their dealings with aliens, criminals, people of a certain gender).
By that last one I mean it can be interesting to decide that your character, normally compassionate to enemies, will not play nice with anyone connected to the Hutt cartels. My female Inquisitor was averse to killing other women, with only a few specific exceptions that she still felt uncomfortable with.
Playing neutral can be very interesting and varied. Power-hungry types can still be gracious to those around them (Palpatine). Doers of good can be stern and unyielding (Mace Windu).