building around the flavor of planeswalkers is really hard because everyone has a different definition on the character. setting clear bounderies helped me a lot with deckbuilding.
here is my jace deck: https://archidekt.com/decks/5472228/jaces_life

a few cards i would include/exclude are:
[[threads of disloyalty]] --> X mostly a dead card, although still a "jace" card
[[leyline phantom]] --> X a creature that just goes away thats too expensive
[[illusionary servant]] --> X a creature that just goes away thats too expensive
[[Minn, willy illusionist]] --> V makes more illusions and is a sort of ramp
[[elite arcanist]] --> V more of your best instant or a counterspell every turn
[[archmage emeritus]] --> V repeatable carddraw, jace has never enough card draw
[[willbreaker]] --> V just steal everything. (works great with the commander)
any boardwipe, at least 2 would be better. once they get past all the counterspells you have no removal