Hi there, would it be possible to add Horse from the Stables in this plugin?

Could you be specific about which options you would like to see? Low grade fuel amount obviously isn't applicable to horses, and the way prices are configured don't make sense since horses are claimed via a saddle which us purchased via a vending machine. The plugin does have a permission for assigning ownership to claimed horses, plus a permission for allowing free horses, but that requires a saddle in the inventory for the claim option to appear, which is not trivial to fix without other complications.

Oh sorry i tried messing around with horse prices

For adjusting horse prices, I suggest using a plugin that edits vending machine orders such as a Compound Options. I'm working on a rewrite for Custom Vending Setup but I wouldn't recommend using the current version of it since it causes lag spikes.