I think you might mean cluttered rather than clustered.
If that's the case, you will want to limit the number of major tick marks. This can be done without specifying the increment c with an axis statement option such as
axis1 minor=none
major=(n=5)
;
If you add order, it might still get messy.
Another option might be to use proc means to find the min & max of the data for each variable and then run the results through a data step to round the min & max values, calculate an increment, and then output them to macro variables. These macro variables are then used in the axis statement, e.g. order=&min to &max by &incr.