Determining Value of Rares

Hi everyone, I come here to ask how to determine values of rares, both of rares I have and one posted on Path of Exile Trade. I know there is awakening PoE trade which does work nicely for my stuff, I assume it works well enough but when it comes to buying stuff off of path of exile trade I don't know what is overpriced, underpriced, a scam, etc. So I want to know how to roughly judge value in gear so I don't lose my precious few EXs.

In short, your question does not have a specific answer. Too many variables.

To accurately price a rare you need to look it up on the trade site with the specific mods and ranges to see what similar items are selling for. Awakened POE trade does this well for you in game (adjust the item's sliders and filter the mods that are important), otherwise use the official trade site.

As far as what is valuable, that is on you. You might really need that pair of boots with triple res, movespeed and life because its the last piece for your build and caps those resists. So you might overpay for it.
Otherwise use the 'live search' feature on the trade site with a buyout option so you get notified when an item that matches the mods you want in the price range you want gets listed.

Here are a couple appropriate videos

ziz
https://www.youtube.com/watch?v=k4qhRzvolLc
path of matth
https://www.youtube.com/watch?v=IVu7mDZRq8s&t=154s