I’m writing with an early September spec call that is easy arbitrage already if going from CardTrader Zero to TCG Direct, and which will also be on the move naturally due to renewed demand from Dominaria United.
That card is Yoshimaru, Ever Faithful. It can be found on CT0 for $2-3 and sold on TCG Direct currently for around $6.
This card is going to show up in many commander lists from the Dominaria United set, including but not limited to two of the most popular ones from the set: Jodah, the Unifier and Cadric, Soul Kindler.
I expect Yoshimaru, Ever Faithful to trend up to $7-8 on TCG Direct for normal copies over the next 6-8 weeks, and the Extended Art to hit or eclipse $10 in that same timeframe.