IMO you'd be best served with a card that pays flat-rate 2% cashback on all purchases. The best 2% cashback cards right now are the State Department FCU Premium CashBack+, the Wells Fargo Active Cash, and the FNBO Evergreen. All three are Visas, and the FNBO card is probably the easiest one to get approved for. All three have a $200 signup bonus. All three pay 2% cashback on all purchases.
The SDFCU card has no FTF and only a $5 minimum to redeem cashback. However, its $200 signup bonus requires spending $3,000 within the first three billing cycles. The Wells Fargo and FNBO cards have 3% FTFs (so they aren't really usable outside the U.S., or for orders from foreign merchants) and require cashback to be redeemed in increments of $25. However, it only takes $1,000 of spend in the first three billing cycles to earn those cards' $200 signup bonus.
The Citi Double Cash remains a solid 2% cashback card, but it doesn't quite stack up to the cards above. It has a 3% FTF. It doesn't have a signup bonus. Why forfeit $200 when one could get a similar 3% FTF, 2% cashback card from FNBO or Wells Fargo or, for a little more effort, a no-FTF, 2% cashback card from SDFCU?