Go back and look at previous years to see who keeps QBs, who keeps 2 QBs, and all that stuff. Get a feel for who keeps what position and what will be available in your draft. If everyone is usually keeping 1 to 2 QBs, I would keep Stafford, otherwise screw that man, save that keeper spot for another RB/WR!
I would keep:
Kamara, Shady, Coleman, Crowell
Brown, Thielen, Gordon
Those 3 WRs you absolutely cannot give up, and as for Graham you will not find any TEs in the draft with nearly as much upside as him (unless someone has an absolutely stacked roster and doesnt want to keep a valuable TE)
Those RBs should provide a good amount of safety. You are essentially eliminating the first 8 rounds of your draft, so RBs will be thin out there.
Basically, in the later rounds of drafts (9+) I find tons of WRs with upside and QBs that are streamable. I would keep the players I listed above for that reason.