Hi Marcy,
If you want to finish in Santiago, do you know how far you'd like to walk each day? You could possibly start in Leon if you're a good walker. Or else start in Astorga, and have shorter days walking, bearing in mind that you'd have the climb up to O'Cebreiro, and you'd be able to break that up into smaller stages.
Have fun with the planning! It's all good..
Buen camino, Helen