If the car is a touch lower on the RHS than the left at both ends (assuming you are measuring to the top of the wheelarch from the ground?) then adding shims will raise the RHS - strangely it will also raise the LHS but not by nearly as much. Although a pain, I would do the front spring first, as you may find the rears are OK afterwards. Only two shims at the front at a time, max, I would suggest. Thinking diagonally, raising the front RHS will put more load onto the rear LHS.