I generally do a wind and waterproof garment over a good (crushable) sweater and maybe two other wicking layers under that.
Are you hiking where water is available on trail?

I can run up flights of stairs here.

My lungs were not prepared for the altitude climb needed in the Grand Canyon.

I felt like I was strangling.

lol. Pathetic sea-level critter

Boots- buy new but break in
Everything else could come from a thrift shop. Are planning on making this a repeat performance?

I have all that stuff on hand , aquired from all different sources : Amazon, thrifts, yard sales etc.

Used to do a lot of hiking and mountain climbing and the most important accessory you need no m atter the climate is good hiking boots. They should be broken in first. Never wear new boots.I have bought boots at outdoor outlets in my area for what you can buy on-line but I would want to try on boots-even though you can return them. LL Bean,Land's End, and EddieBauer all have mail order. Since I've been outdoors person for years I'd skip long johns unless you go camping in snow. Layers are the key to hiking. Down vest not jacket. For socks and flannel shirts I go to my closet.

You need to be sure your boots fit and good socks.

Absolutely number 1: I shop locally for what I want, then find it online at campmor.com. Is that cheating? I buy men's socks and flannel shirts, but hiking boots (which reminds me, I need a new pair) are custom made for my feet at that local retailer. No matter what, hike naked, whatever - boots are the most important thing, and I will pay a good price for them. You get what you pay for.