From Diablo Wiki
Training is the process of upgrading the Artisans. Each of the three Artisans has ten skill levels, and as they increase in skill they gain new titles and learn new crafting recipes and plans.
Their appearance improves as well, with their wagons growing more elaborately-decorated, and more cool stuff appearing in their displays.
Training an Artisan is not free; each level requires progressively more materials and gold.
The gallery of images below shows the spot in the Hidden Camp in Act II eventually occupied by the Mystic. You see before she has arrived and then each of the ten stages of her training as her wagon grows ever grander as her skill increases.
|Items of Diablo III  Item Basics Normal Items Legendary Armor I Legendary Armor II Legendary Weapons 1h Legendary Weapons 2h Item Sets|
|Item Basics||Item Modifiers||Inventory||Artisans||Merchants||Miscellaneous |
|Armor - Class-Specific||Weapons - Class-Specific||Crafting Items||Other Items |
|| • Blacksmith Plans
|Waist||Wrists & Hands||Legs & Feet||Head |
|| Voodoo Masks - WD|
| Chest Armor
|| Amulets cont.
|| Rings cont.
40) Puzzle Ring
|| Sources - Wiz|
|| Fist Weapons - Monk
|| Mighty Weapons - Barb|
|| Daibos - Monk
|| Bows |
|Diablo 3 and Reaper of Souls Item Sets||Reaper of Souls only |
Torment-Only Class Sets
Torment-only Themed Sets (Not class-restricted)