Here G1=1/2(-3dB) F1=2(3dB) G2=100(20dB) F2=2.5(4dB)
G3=1/1.58(-2dB) F3=2dB
so F=2+3+.012=5.012(7dB)
so if u want to reduce overall noise figure of ur Rx use low loss first component and also use high gain LNA the rest of component will not affect the NF much.
If you didn't take care of the NF in the LNA stage itself and even before it then, there is not much you can do after the LNA cause NF is additive. If you produce a poor NF, you will not be able to fix that.
using optimum gamma of the transistor datasheet if it is uncinditionally stable or near it as much as possible if it is conditionally stable and use optimum dimension for stub and transmission line at input and output
If you didn't take care of the NF in the LNA stage itself and even before it then, there is not much you can do after the LNA cause NF is additive. If you produce a poor NF, you will not be able to fix that.
RF_Router is right. First stage is the most important stage. After that there is nothing you can do. LNA must be stable also in your range of frequencies. In contrast as it helps NF is that oscillator must be very unstable.