There's for sure not really a rule. From what I observed, you need a pretty high level of awareness (a known game design, a known studio or known game designer would help) and a good presentation.Then you should consider the uniqueness of your game, getting money as nobody for the 100th minecraft clone is much more difficult then to get money of some unique idea. And least but not last, the cash goal should reflect the value of the game, nobody is willing to pay you 1-2 years of salary for developing your game idea.
So, my two cents with the background, that you have no reference games or a name known in the industry:
- Choose a unique game design.
- Make a kickass presentation.
- Best to provide a playable demo.
- Choose a reasonable goal.