hmm...
I will say if you have taken CAT before (seriously) so you have a fair idea of what it is and by now should be comfortable sitting for 2 hrs and indifferent to difficulty of the paper and no of sections in it. If that is the case then taking 1 AIM (all india thing is imp. as it gives you the fair idea of you relative performance) per week is sufficient. Though you can take as many section tests as you like depending on the things you are looking for from those section tests.
But if you are a first timer then i'll suggest giving 2 mocks per week. But the most important thing is analysing that paper. You have to sit for the paper for 4-5 hrs (av fresher time) analysing where you not only solve all the questions but also (infact the more imp. thing) think about the questions you solved correctly but took too much time or sitters which you missed. Think how to avoid the situations like these. Identify your stronger and weaker sections. Infact not only that try to identify your stronger and weaker topics inside those sections.
As i read in 1 of the topics last yr (when i was a fresher myself) that its better to get a question wrong in 30seconds then to have it correct in 3 mins!!
Enough of this gyan

I hope you got what you were looking for....