The Prosecution at the ICC has recently submitted a Report which provides information about its structure and resources and allocations at each stage of a case (see especially p. 52 et seq). You can access the report by clicking the link below the image:
http://www.icc-cpi.int/iccdocs/asp_docs/ASP14/ICC-ASP-14-21-ENG-OTP-BasicSize-07Aug15-1103.pdf
Image source: www.es.amnesty.org
Text source: Xavier-Jean Keita