In Middle Earth Shadow of War, Talion has quite a lot of skills to upgrade and those skills themselves can be upgraded. This will show some of the skills, particularly in the initial part of the game.
Probably the most useful skill to unlock early in the game, especially when facing large number of orcs. Run to the nearest campfire and set off fireworks.
Next, consider the stealth approach from a distance. Use poison arrows from a distance. The Poison Tendril Skill.
If you are looking to stealth attack 2 enemies at once, use the skill Wraith Chain. Add in the elven rage attack, and Talion will be unstoppable.
A useful skill to unlock early – Execution, but probably best for Captains which can be eliminated straight off with execution, or Captains who are fearful of execution.
The caragor rider skill is quite useful as the map gets larger and Talion needs to go from one place to another really fast.
The Brutalize skill is very useful when Talion needs to use stealth and disperse a certain number of orcs.
Then there are the story main quests skills which keep unlocking as one progresses further into the story. One of the best is to summon followers.
Later Talion can dominate more types of beasts, including Draugs.