Virtually everything you pick up can either be used as an ingredient once you unlock the ability to enhance armour (since you're reaching Kakariko, you are very close to doing so), or they may be required to be given away in large amounts to complete various side-quests (almost always for Rupees). In my opinion, do what Phendrift said with the Guardian parts, but the game somewhat scales your ability to improve your armour based on how far into the game you are (or to be more accurate, how much of the map you've explored), and practically anything you've likely managed to dress yourself with can easily be upgraded with stuff you find between the Plateau and the village. Sell the gemstones, any trip along a mountainside will yield more.Guess it's better to ask here
I'm still at the start of the game and reach Kakariko village, what is safe to sell? I've got some gemstones and mechanical scrap.
Edit:
Thanks for the info mate. I'm bound to find some more gemstones over time so I could sell some for now and get some equipment.
Also, if it's more the need for cash that is limiting you right now, do a round of hunting and foraging anywhere between the Plataeu and the forest near Kakariko and make some decent healing meaty meals, they typically sell for a bit more than the sum of their parts, and you'll be almost guaranteed to use ingredients that are in no way precious later on.