We present the methodology for designing the optimal gain profiles for slow-light systems under the given system constraints. Optimal system designs for the multiple Lorentzian gain lines make the gain spectrum uniform over larger bandwidth compared to the single-line gain system. The design procedure for the multiple-line gain systems is modified to make the gain spectrum uniform over arbitrarily broad bandwidth and applied to the design of the gain-only and gain+absorptiou slow-light media. The optimization of the triple-line gain system improves the delay-bandwidth product 1.7 times the delay-bandwidth product for the single-line gain system. For the broadband slow-light system, the optimal gain + absorption design and the optimal gain-only design improve the fractional delay performance by factors of 1.8 and 1.4. respectively, compared to the Gaussian noise pump broadened (GNPB) system.