You need to make some assumptions to get all the values (like for example setting L to a certain number and sticking to it even for M1. You also need your gain equation which will be given by vout/vin = -gm1*rds1||rds2||RL. gm1 is gonna be a function of Id1 (which should be equal to IQ to center Vout at midrail), W and L of M1. By setting Vout to 0 you have Vds1 (DC) which allows you to set a reasonable Vdast number (depending on linearity specs) which will finally determine Vgs1. As you add more and more constraints to your design your number of equations increases and allows you to select the appropriate values of Vgs2, W1, W2, etc to meet those specs.
Hope this helps,
diemilio