I worked a long time at coming up with a skill tree that works for what I want.
*It should allow to build a specialized character with some deepness
*It shouldn't be overcomplex/frustrating/overly limiting.
*It should support players to search for ways that don't involve finding
*...but still offer an interesting and challenging gaming experience.
*It would be great if it would be still possible to balance
These things sometimes seemed contradictory to me. But after reworking it over and over, I believe I came up with a satisfying concept:
Short explanation:
-The four main arms are correspondent to the attributes (Power, Dexterity, Intelligence, Intuition) each character/enemy has; when a check is done, the basic strength of the players "attempt" is generated (e.g.: 30 Intelligence)
-The branches descending from it (e.g.: Craftmanship, Constitution, Magic) are the skills. These start at x0.5 and can be upgraded up to x2 (so, a player with x0.5 on "Craftsmanship" who has the 30 as base value would end up with 15 in their check, while a player with x1.5 would have 45, and so on).
-The smaller branches are specializations. They default at x1 and can be upgraded up to x2 or x3 (This will require some testing) - they can be only used if the task at hand kinda fits the specialization (e.g.: The aforementioned player could convert his craftsmanship-check of 45 to 90, if they had a x2 specialization on Metal). The DM should estimate higher numbers (-> difficulty) for specialized checks. Players can ask for further specializations and learn them - either for the main branches if something needed for a character or a campaign is missing, or improving existing ones (e.g: A player could, after discussing it with the DM, add the specialization "gold smith" after "Metal" to receive further bonuses).
If you can use this skill-tree or any of the ideas in here, feel invited!