Some links here will help to explain.
It's all about points, and stars take into account the undyed points and the dyed points. This is why we ask people to provide the undyed rating, otherwise everyone screams 'I got a 3*/2* with this random piece of equip I have!' while all it is, is just a 1* undyed item that got boosted by the dye to the 2/3* point bracket.
ANY equip in themed slot give 1* = 2 points.
Give it the correct family dye, it jumps to 4 points.
Give it the best dye, it jumps to 5 points.
Translate it back to stars - 4 point is 2* and 5 point is 3*.
Also the other thing we keep hearing is 'I got multiple gold item, but I can't reach 80 points' - well that's because their gold is post-dye. We don't consider those true gold items, they're just 3* or 4* boosted to gold, and therefore still can be missing a lot of points.