Title speaks for itself, I’m making a game very similar to Isle - Roblox
My main thought was I should make the tools and items first but now I’m wondering if I should work on the map and locations first and some core components like background music based on location.
Anyways, If someone could help I’d appreciate it.
In my opinion, you should work on the map/story first, but only after you’ve come up with 3-4 other ideas and decided that this is the best one to go with (don’t want to switch half-way through for a better idea). The story will really determine what the map, tools, and music should be.
Hope this helps!
If it were me, I would start making the tools & basic mechanics of the character like sprinting or hunger & thirst maybe, along with basic UI(Nothing stylized, just something to get the job done for the time being). After that, I would start making assets for a game, kind of like a kit that you can always go back to when it’s time for decoration and map design. Then I would start working on things like background music, terrain, and decorating.
Good luck on your game! 
One method to make a good game (in general) is: you have to make something new, or improve on the old.
Now, since you are making a game similar to Isle, what did you think was bad in the game? Did you see any bugs? Try to improve based on this.
This is your game, though, and it’s your choice, so I’m not giving specific ideas.