Which feed missions have you completed? The following are the ones that I think are definitely worth getting.
Fielder
Ichiro
Papelbon
Wagner
Bautista/Holliday
Gwynn
Beltre (although won't be necessary if you have arenado and machado)
I'd say Molina is worth it if you can find one at a semi reasonable price since he's the best defensive catcher. Although I would not recommend paying 200k+ since you already have Bench, and it's tough to find Molina under that price.
I'd recommend just waiting until you see a new flashback you like, since some really good ones will come out eventually. I'm sure some great cards will come out for just about every position. I know I'm looking forward to some of those cards on the leaked list