best optimization tool to use

Hello I am looking for the best way to optimize systems variables based on measured data. I have an electrical one port network with four variable discrete capacitors and couple of fixed inductors. I am continuously measuring (acquiring S11 from network analyzer). At a given frequency, what is the best optimization tool to find the optimum capacitors values that make S11 meet a certain goal (i.e. S11 < -3 dB). So I start with initial cap values (C1, C2 C3 and C4) read S11 from network analyzer, feed these values to the optimizer function, get a suggested new values of the capacitors , re-measure S11 and repeat till S11 meet the goal and get the optimized cap values Thanks for your help and suggestions in advance.