Exp item turn in path from level 1
 

How high could a character get in theory without hitting a mob by just turning bone chips, belts, pads, goblin ears etc. (without the exp turn ins getting so low it doesn't make sense anymore)

What would the path be? I.e.
1-4 bone chips
5-10 cb belts
11-15 cb pads

What am I missing and what is the optimal levels to switch to the next item?

Orc scalps in high pass

left goblin ears in highkeep

Goblin ears, deathfist slashed belts, lightstones/greater lightstones

You can do 1-9 with bone chips if the dorfs like you.
9-15 belts and pads.
15-20 orc scalps
20+ goblin ears.
30+ sarnak braids but they are no drop and you have to be able to turn them in atthe outpost.

Lightstones and greater lightstones are good from 12 up to at least 17. If you can find a seller for the GLs, it ends up only costing 5g per stone.

Keep in mind there is a % cap on xp gained per hand in so if you are handing in these things too early you are wasting potential points of xp.

Some items might yield better % per turn in, but for availability its hard to beat kaladim bonechips until level 16ish

No wonder why my last turn in of belts at level 1 felt so awful. Any more info on this regarding min levels for optimal ROExp

This and this.