This one can be done a few more ways too…depending on how you made the text and how detailed it needs to be…
-first I would try using a text spline in a sweep nurbs and keyframing the “end growth” in the attributes.
This works well with some fonts but not all.
Or
the next thing I would try is animating the Alpha channel in the texture…this is not so bad with square fonts but can be boring to do since you are playing with a gradiant and it is very dependent on the texture…ect.
There are more ways but these are the two i would try first.
/Randy