After completed a lot of things I understanded that I missed a lot of content. For example I did a stupid mistake and sold potions, gold nugget early game, didn't let bosses do things with me, and much more. I didn't completed the game 100%, I will wait the next update. I know is already on patreon 0.94, still tho.
If you sell anything important, you can buy it back again in the evenings from the trader's tent in the town.
And there is generally no time limit on any actions. You can't really "miss" anything. Just keep interacting with the same person until you trigger the events that progress the story. Some events have to happen before others become available.
Check out the character pages on the wiki (see the game's home page, linked above) for some details on their progress paths.