There is no universal standard for determining what score you need. For example, colleges do not have the same expectations of their new students when it comes to readiness, so an EdReady score of 70 might be high enough for one school but too low for another.
You can evaluate whether your score is good enough by examining your score on the Target Options page where your score will be placed in context with the schools you would like to attend. Note that an EdReady score of 100 means that you have demonstrated mastery of all of the material for that study path; it is not possible to get a score higher than 100 in EdReady.