PCB design for 50MHz
At 50MHz, the wavelength in the PCB is about 20ns x 15cm/ns = 300cm.

The time of travel in a wire of 30cm is 2ns.

If you want to avoid to consider you traces as transmission lines, you must keep them under 1/20th of the wavelength, which is 15cm.

And at that length you need to account for the 1ns signal delay when checking hold and checkup times.

You also need to avoid crosstalk between parallel wires by keeping them 3x their width apart.