Hey ho! I used Ink for this + Inkle's unity ink integration + my own custom framework thingie I've written over a long period of time. Honestly it's almost cheating (they did allow tools though! and this is definitely a tool!). I heartily recommend Ink, it's free, used in actual real games (Heaven's Vault, 80 Days, etc), and super customizable. I've actually got it in a repo here: https://github.com/wolfrug/inkwriterdev
Although I always customize it a little bit extra for every game I make, so that's really more basic. It does have the inventory system though :)
And thanks!