When i started out in the outdoors I was pretty cheap on my clothing, but after years of spending time in the outdoors and mountains, I find that proper clothing makes a huge difference and it's worth the money. Do note that more expensive does not mean better, some cheaper brands can have very good clothing too.

Proper clothing that is well ventilated and prevents excesive sweating and wicks away/dry sweat quickly makes a huge difference in how it keeps you warm. I prefer synthetic materials as they dry quickly and are light weight. Mesh, breathable panels and vents are great in making clothing adaptable.

A down jacket services as a good compact and light weight option in case it's colder than expected and is your emergency insulator when you need to sleep. In some cases I replace it with a good microfleece, as that give me a little beter freedom of movement. Put your legs/feet in your backpack to keep those warmer. My clothing is sized that I can put on all my layers on top of each other when needed.

My emergency sleep system is a down jacket + bivvy + handwarmers.

Poncho's just don't work for me as rain gear, catches too much wind and can't see where you are walking properly.