Starting team

1 Blitzer 100,000gp
1 Witch Elf - 110,000gp
9 Linemen - 630,000gp
2 Re-rolls - 100,000gp
6 Fan Factor - 60,000gp

With this starting team, you should be able to handle any threat your opponent may present. Designate one of your linemen to be your throweruntil you can buy a real thrower.

Offensive Tactics

Pile up one side of the pitch. Put 3 men on the line, 2 on one end of the field, 1 or 2 in the backfield, and the rest on the 2nd side of the field.  Break a hole in your opponent's wing and blitz through with as many people as you can, making sure to stay near but not ON the sideline.  You can use your Witch Elves to catch the ball, but they are also well-used as blitzers, to knock holes in your opponent's wing.  Pick up the ball and stay a safe distance from the line on the first turn.  On the second turn, run up and pass it to a safe player (preferably a blitzer) i.e. one who will not be hit easily should you fail.  Next, if your opponent has people in front of your block, blitz a hole and run through.  If he doesn't, then the touchdown is yours.

Defensive Tactics

Elven, Human, or Skaven Opponents

Put 3 men on the line, a blitzer and a witch elf (or a reasonable substitute, preferably one w/ Diving Tackle) on each wing, and your thrower in the backfield with at least 2 other players.  Your opponent will almost certainly break through one side of your defenses, so make sure your defense is symmetrical (i.e. neither side is weaker than the other), because these teams are as good at piling one side as yours is.

If your opponent breaks through the line, and it is possible to get your witch elves into a Blitz position, frenzy one of their catchers off the field (this is assuming your opponent's QB has held back out of range for your witch elves to blitz; if he is within range, do not hesitate to
take him down).  Make sure to get your backfield in front of any other catchers that may be out there.  Next, blitz in with your witch elf and blitzers.

Your opponent should not be able to find a hole in your defenses now.  Unless he is very lucky, he will be unable to score this turn, and if this happens, your team should be easily able to recover the ball and launch it downfield to a blitzer or witch elf behind enemy lines.

Strength Teams

Put 3 men on the front line, your witch elves and blitzers on the wings, and your other players safely back behind the line 2 or 3 squares.

Your first order of business is to blitz their runner or thrower with your witch elves.   Secondly, try to avoid open confrontation (i.e. dodge away from his line).   This will hinder your opponent's ability to advance "Da Crunch", "Da Cup", "Da Bloc", or whatever your league calls it.

Get as many people as you can behind the lines, but make sure you have at least 3 in front of the enemy, and enough on their flanks to prevent them from cutting to one side of the field.

Assuming your opponenet is not extremely lucky or skilled, you should be able to acquire the ball within a turn or two, and then you can outrun most strength teams straight to the end zone.

Skills

Witch Elves

1. Block: Your witch elves will need block to be an effective player on your field, whether you mean them as catchers or blitzers (or both).  With this skill, your witch elves weakness of a 7 AV becomes less of a hassle, and it is more likely that you will be able to knock over most of your opponents w/o being knocked over yourself.
2. Dauntless: You will undoubtedly encounter members of an opposing team who will be stronger than you (especially if you are brave and are playing an elven team in a strenght-based league).  Dauntless will allow your witch elves to frenzy your opponent into the crowd on a 1-to-1 basis, and with block, you should not have too much trouble doing this.
3. Pro: Pro will allow you to reroll those nasty skulls, or even failed AV penetrations or foul rolls.  'nuf said.

Other usefull skills: Leap, Strip Ball

Blitzers:

1. Dodge: No elf should be without it.
2. Catch: How else are you going to get those long-bombs?
3. Dauntless: Even though you may use your blitzers primarily as catchers, you can never have enough people behind the line, and given their MA, your blitzers are your most likely candidates aside from witch elves.

Other useful skills: Sure feet, leap, sprint, frenzy.

Throwers

I agree with the BBC suggestion here. As soon as you can, form an offensive and a defensive thrower.

Offensive Thrower

1. Safe Throw
2. Accurate
3. Sure Hands

Other useful skills: Dump-off, strong arm.

Defensive Thrower

1. Dodge
2. Nerves o' Steel
3. Accurate

Other useful skills: Safe Throw, Sure Hands, Leap

Linemen

You should have 3 basic types of linemen: Linemen (a.k.a. Black Orc fodder [though you should, with time, be able to teach those nasty Black Orcs a lesson they won't soon forget]), Dirty Players (a.k.a. 'dem Bastards), and Blockers (a.k.a. that Cheater!).

Lineman

1. Dodge: No elf should be without it.
2. Block: So you can't be knocked over!
3. Sidestep: You can chose where you're pushed to or knocked over.  This is good because your bodies can hinder your opponent's offensive strategy.

Other useful skills: Guard, Dauntless.

Dirty Players

1. Dirty Player: 'nuf said.
2. Pro: Reroll those nasty failed rolls.
3. Block: So you can knock 'em down AND foul them... a nasty combo.

Other useful skills: Dodge, Dauntless, Frenzy.

Blockers

1. Diving Tackle: Stop them from breaking through your wings.
2. Dauntless
3. Block: easier to knock them over and prevent them from breaking through your wings :)

Other useful skills: Dodge, Mighty Blow, Guard.

Other Tips

Even if you are a "nice guy" and don't foul very often, if you're playing against a wood elf or high elf team... for God's sake foul as much as you can! Its your purpose for being on the pitch for that game (aside from winning, of course)!