If you're prepping for Basic Training, then rucking makes sense. Wear the boots, as well, you need to get your legs used to the weight of the boots.
If you're not prepping for Basic, then I heartily agree with the others who recommend learning to backpack light. I also follow the BPL forum previously recommended. One- get a pack that FITS your torso. I only found out last year that they make packs in different torso lengths and that gender has little to do with it. I'm a woman with a 21" torso (average woman is 15"-17") so I need a pack designed for a very tall person. If my pack is too small for my torso, I end up carrying all the weight of the pack on my shoulders, which is no fun. A well fitting pack will carry the weight on your hips. Your big 3 items (pack, shelter, sleeping bag/quilt) should be under 3# each max. Check out BPL and also hikelight.com for more info, if backpacking is your focus. Study up before you buy- otherwise you'll be like me and buy something only to find out that there was something better and buy that too. Ha. I could outfit 3 backpackers right now.