Go to a sporting goods store that will measure you and properly fit you to determine your pack size. If your gift pack is not that size, ebay it and find a pack that fits you and will carry your gear without wearing your hips raw. I have had difficulty because my size is small in some brands and medium in others - those 1-2 inch differences make a huge difference in how it sits on my back.

I'm sure you'll find a zillion tips and tricks for gear on this forum. I found a group of day hikers on meetup, and within the group I found some "like minds" to go on backpacking trips with.