I think my conclusions about equipment these days, is that, rather than think of single items to purchase I now think in terms of the purchase of group items. So for example, the bottom half is about trousers, waterproofs or rain skirts, gaiters, socks and boots. If you get them right and they harmonise together the hiking experience is so much better. We know this about the torso layer systems, baselayer, middle layer, gloves, hat or hood and the waterproof outer, etc and I, for a long time tended to concentrate on this without considering much else. But I then gave a lot more thought about my sleeping gear, because in my early hiking days I was often cold. I learned that product harmony here also matters, groundsheet or footprint, tent base material, matress, sleeping bag or quilt, when the products work well together then I am well. In a smaller way I also found that even my underwear and baselayer needed thinking about, I hated it when a skin gap occurred between m the bottom of the baselayer and the top of the underpants elastic. I now always buy long products that can tuck in or overlap and will not ride up as I walk.
When I first started 'proper' hiking I underestimated this harmony link but nowadays (after a few purchase blunders) I think I have now got it, just about right. What I have never moved onto is hiking and camping in extremely cold areas and with prolonged periods of darkness, if I did I'm sure I would have to have a rethink.