The problem is that in most of the world, the word "backpacking" means budget travel with a pack on one's back. Only in the US (and maybe Canada) does "backpacking" mean multi-day hiking on trails in the wilderness ("wilderness trekking" to most of the world). That's why we need to know which definition our young friend (welcome, freeexplorer!) is considering (maybe both?) so we can give appropriate advice. Just as one example, the lightweight backpacks most of us use for wilderness backpacking are not designed for the rough treatment given by airline baggage handlers, so recommendations for a pack would definitely be different for the two types of "backpacking."