I agree that 11 players to start is fine, but I disagree with Ullis about throwers not being useful. The thing is that they can free up the Gutter Runners to wreak havoc on the other team up near the line, instead of sitting back to get the ball.
Now that you don't have to worry about FF as much, you can actually make a pretty good 11 rat roster that has it all:
2 Throwers 140
4 Gutter Runners 320
2 Blitzers 180
3 Line Rats 150
3 RR 180
30k for FF or CL or AC or save for apoth
Then all you have to save up for is an apoth and the Rat Ogre.
That roster is tough for most other tv100 teams to cope with. Lots of speed, Gutter Runners all over the place. Alternately, if you like playing a little crazy, you could try to work a rat ogre into the starting lineup. I've done that for TV100 tourneys and done pretty well.
1 Thrower 70
4 Gutter Runners 320
2 Blitzers 180
1 Rat Ogre 160
3 Line Rat 150
2 RR 120
Like I said, it's a riskier roster, but it can be fun too. The Rat Ogre helps control the line, as long as you don't count on him for anything (never blitz with him), helps keep rats alive, and even gets a cas now and then to help keep the numbers more balanced. That in turn makes those gutter runners (still the heart of your team) even more potent.
But only 2 RR is rough. In the tourney, of course, you can give leader to the thrower, so you're back to 3, but in league play you have to build to that.
As far as development, I agree that block is generally the first skill to give them, then I tend towards sidestep, as it helps keep them alive AND makes them better on defense. I also try to get one Leap, it really alters the way your opponent has to defend you, and as Ullis said, build a one turn scorer if you get the opportunity.
Blitzers need Guard first, it is the main reason you buy them really.

After that, skills like Tackle, Dauntless, MightyBlow, and Juggernaut are nice.
I specialize my throwers in league play - one for offense and one for defense. The offensive one gets Accurate and Kick Off Return, on Doubles get Extra Arms to pick up on 2's. The Defensive one gets Leader and Block, as well as Kick if you didn't give it to a linerat already. Doubles go with Big Hand to pick up the ball in tackle zones. Always wanted to try Hail Mary Pass on that thrower too, but never got around to it. Just throw the ball to the opposite end of the field and count on your speed to beet the opponent to the ball, or at the very least make them start over on their offense, but haven't tried it yet.
Linerats generally get Block and Fend if they're lucky enough to live long enough to get 2 skills. On doubles I'd consider Foul Appearance.