If you cant solidify in base white, Id recommend following the best multicolor cards you see instead
The first is a decently sized 6/6 Samurai for six mana
Three main ways: going wide with tokens and an overrun or Coat of Arms, draining the table with Gray Merchant of Asphodel and aristocrats triggers, or grinding opponents out of resources through endless recursion until they cant keep up
Army of One is all about the Stagger mechanic, teeing your foes up for double damage while also offering lifelink, first strike, and trample in a three-cost card
On the other hand, the Commander 2013 and Commander 2015 sets are still easily available for less than MSRP
There are two cards featuring her: Yuna, Hope of Spira which can be found in the Main set, and Yuna, Grand Summoner which can be found in the Commander Deck