Joy,
Two bits of advice (which are not entirely consistent with each other):
1) Generally, the pack is that last thing you buy. You do not want to carry a bigger pack than you need because it is the heaviest item you will carry. My wife carried a 26L osprey; I carried a 28L osprey. This is only not true if you commit buying a pack in that size range 26-28L as a strategy to force yourself to take less stuff (which, you will want to do).
2)A Jade 38 is almost three pounds. Look at the small American manufacturers. They have the best, lightest gear on the planet right now. You will not find them in REI. Look at Zpacks (what my wife and I now carry--about 1.5-1.75lbs, and that is because we went with the more durable fabric. Cuben fabric is lighter and would last for one Camino), Gossemer Gear, Hyperlight Mountain Gear, Laurel Designs, Elemental Horizons, and ULA. Basically, you can cut your pack weight in half.
This is the part that is somewhat inconsistent: those manufacturers have long lead times, sometimes months. So you may need to order a few now, get them, try them out, returns the ones that don't work. These small manufacturers are all real good at returns/customer service.
Buen Camino,
Jo Jo