Don't underestimate the importance of a good K/P as well. IMO it's the one other position on the field (other than QB) where they can single handedly change a game.
If you have a kicker that can rattle off 50 yard field goals it changes the way you look at the field in terms of where you need to get. Field position changing punts are huge as well.
Running backs when in the open field can be HUGE playmakers, but they rely on their offensive line for true effectiveness. If your Mid Tenn St. line is all rated in the 60's and you're playing a team with DE's/DT's in the 80's and 90's that stud running back won't be finding many holes and will be having to make his first move in the backfield.
This is the order that I take when trying to build a program:
1. Gamechangers: QB's and K/P - recruit a QB every year and K/P every 2-3 so you can redshirt them before they have to play
2. The Trenches: Recruit multiple offensive and defensive lineman. Even guys that are 1-2 stars coming in can be effective by the time they are redshirt seniors, you just have to build depth (would be huge if they expanded rosters!)
3. Defense - Focus on filling in other positions on defense. I usually try to get 1 really solid linebacker and then 1 really solid safety in the hopes that they can compensate for the CB's and other LB's. Obviously you want to add talent there, but getting 1 solid player at each level is key
4. Running Backs/WR's/TE's - usually pretty easy to pick up an RB or WR, so just pursue ones that have you as their #1 school until you start to build up the program. If you have a solid offensive line even a 60 rated RB can get yardage. You won't have a back or receiver who is going to bust a 70 yard TD, but guys that are effective in an offense
With the game set up the way it is you have to over recruit and then cut guys. Ideally you will be able to pull in better and better prospects from year to year so you might have to cut guys from previous years. This would be different if there were full 85 player rosters, but at 70 you really are only able to pull in about 14 players per class if you are redshirting your freshman.