thats exactly the point u already have MJD and J. Charles also a top QB i would definatly pick one of those top WR with ur first pick for me it would be White or Wayne , i know austin put up gr8 numbers last year but i have lil doubt he can repeat this but ok we'll see .
but again with what u already have so far now i'd go with one of the WR for ur first pick , its a PPR league so MJD is gr8 already , so one of the top WR would be my first pick ,u can find another good RB later maybe Slaton or so hes ranked quiet low this year and he should be ok espacially for PPR
MJD is great and Charles has more value in a PPR than in NONPPR.
Mathews is an unproven rookie and had limited catches in college (19 if my stats are right) and Mendenhall had 25 catches last year, so you can probably find comparable value at RB later in the draft.
I think you do need to grab a top WR. In my book the top 3 are Wayne, White, and Marshall.
Wayne is the most proven commodity. He's good for 100 receptions plus all his yardage and TD's. The only drawback is his age since this is a keeper league. White and Marshall are pretty equal. Marshall typically gets more receptions, but he is in a new situation in Miami so there's a couple question marks. I think Marshall has the higher upside as I look for Chad Henne to have a good year.
I'm going to agree with your assessment that you do need a WR1 here. While Matthews is tempting, we don't know what he'll do yet. And picking at 2.12 will give you table scraps for a No. 1 WR. I'd say go with White. He's young and has a ton of upside. Wayne has been a model of consistency but he's getting old and he's mad about his contract. Gonzalez, Clark, Garcon, and Collie will cut into him too.