Guys, OP is 15-17. This drastically limits where he can go. He can't exactly go to a 3rd world county where he can't even speak the language. He is looking for a backpacking type trip where he won't have to interact extensively with society.
OP, Denali is a poor choice for you. Are you planning on a summit bid? You will need a costly permit to do that, along with a lot of technical know-how, not to mention climbing partners. Gear you will need:
Crampons
Crampon Compatible boot
Snowshoes/AT skis
4 season tent
Lots of outerwear including a high-altitude setup such as a Mountain Hardwear Absolute Zero Down Parka & matching pants
Really nice sleeping bag
Piolet
Pulk
This doesn't even get into all the regular gear you will need like a stove to melt snow and cook on, ropes, etc etc.
To outfit yourself for a Denali summit bid is going to be around 5K in gear. Plane ticket should come in somewhere between 1-2K. I'm not sure what current Denali permits cost, but I know they recently went up in cost quite a bit. Your biggest hurdle will be finding a team to climb with, as well as acquiring the necessary high-altitude mountaineering skills (self-arresting, etc).
If you are not going to climb McKinley, the gear you will need depends a lot upon the time of year. Make certain you research bug season. Life in Denali NP can be hell when the bugs are bad. Sure this is a good idea? BTW, Denali will be a far-cry from Philmont. At Philmont you need absolutely zero skills or know-how, the trails are easy, the supplies are taken care of for you, campsites are pre-selected and pre-prepared, you never cover much daily mileage, water sources are known in advance, and you always have someone telling you what to do.
My advice? Take on a mellow backpacking trip by yourself, somewhere less than exotic. Why not hike a section of the Appalachian Trail? If you have a longer time window available, a thru-hike of a smaller trail would be an amazing experience. Think about the John Muir Trail or the Long Trail. Allow approximately a month each for them. Cost will be minimal, you probably already have some of the gear you will need, and you will have accomplished something.
