After 10 years of playing, I finally decided to learn about NPC skill trainer limits. You can train 5 total skill points per level. Power train early by talking to a trainer
Skyrim Magic Spells and Mage Builds Guide - SegmentNext
Skyrim - The Complete 50 Skill Trainers of Skyrim - Just Push Start
Skyrim Levelling and XP - how to power-level every Skill to Level 100 | Eurogamer.net
Skyrim Restoration Magic & Spells List
Where is Master Alteration Trainer - Skyrim - YouTube