I already have some mods to fix basic things and don't need advice on that, but I'd like to know about leveling in the game. Apart from knowing that you can't level everything, I don't know much about it, so I have some questions:

• What stats/skills are useful, useless, or depend on the situation?
• Do I need to have a specific build in mind or can I experiment to some degree with stats/skills?
• Are there difficult parts of the game where leveling something for it helps make it more tolerable?
• Do you spend points when you get them or save them up for something, or both?

I'd like to thank you in advance if you're able to answer my questions or explain something I might not have understood!