Is there a certain amount of titrant that is ideal?
In a perfect world there would be no optimal range. We do however live in a world full of errors and practical considerations.

Why use over a minimum amount?

Let's assume for demonstration, that each drop has a volume of 0.05 mL. Of course this is not an accurate value as various factors would affect this. 

The titration has reached its end point when one last drop changes the colour. If your titre value is very small e.g. 1 mL, then each drop is 5% of your titre. 

If only part of the drop is needed to reach the end point then all the extra part of the drop is inaccuracy, which in this scenario could be up to 5%! If you have the misfortune of accidentally adding one drop too many you are introducing an even larger error. This will impact concentration calculations based on the experiment.

Why not just use 'a lot' then?

There are a couple of things here:

1) As noted by Mithoron, this would be a waste. The accuracy gained from requiring additional titrant will level off rather rapidly.

2) If you use more than one full burette's worth there is an error penalty.

3) Using extra titrant is a waste of your time. Consider a 50 mL burette, if it needs to be filled up after each titration, that would be inefficient. I'm assuming you're doing repeats so this has real merit.