The route "via Craven Arms" tickets from Birmingham Stns to/from Ludlow, priced by TfW, don't have any time of the day restrictions and are priced at £40.20 for an Off Peak Return or £39.00 for an Anytime Day Return. That's what you'd need to travel via Shrewsbury. Don't think that any Break of Journey is permitted, however, on the Off Peak Return. The prices would of course be reduced with a valid railcard.
The route "Any Permitted" tickets priced by West Midlands Trains are £32.20 for an Anytime Return, £28.60 for an Off Peak Return, £27.70 for an Anytime Day Return and £26.90 for an Off Peak Day Return. These are what you'd need to travel via Hereford. N.B. The two Off Peak tickets mentioned here are only valid midweek at or after 0900. Similar railcard reductions possible.
Seven day season tickets are priced at £155.80 for the "via Craven Arms" variant and £130.80 for the "Any Permitted" variant, so you'd need to be travelling four or more days per week for these to be value. No railcard reductions normally available on season tickets.
Edited: In view of the helpful comments below regarding valid routes. Birmingham to Ludlow via Hereford is c. 78 miles, via Shrewsbury and then Craven Arms it's c. 70 miles.