The most easiest way of getting lots and lots of skill bills is very simple all you have to is:

1) start a 2 player game

2) perform 3 pananas on all of the opposition exceped the keeper (x3)

3) pass the ball to a person on your team do another panana (x4)

4) pass the ball again to another team member not the one who has already done 3 pananas

5) perform another which is the last panana (x5)

6) and a taunt move (my fav one is "TOP 'O THE WORLD" (L trigger and UP on the D - PAD))
Hold this for a very long time (i held it for about 2 hours while I was watching a film)

7) score any way easier to score by a game breaker
And then update your player (i got mine up to 95 with one go at this and a very sore thumb)

To REALLY get skill bills (s.b's) Go on a friendly match On 2 players (so they wont tackle you) and chose trick points and set it to get 1,000,000 skill bills then in match get a Times 5 combo then do any taunt you want ( I chose Teaser ) un till it says some thing like 200,000 trick points then go in gamebreaker then have a shot it will show some thing like 200,000 times and you will win the match and you will get 80,000-130,000 skill bills

I know a way to get loads of skill bills..
Go on to a friendly game. Select controller 1 for your team and controller 2 on the other team. Set the goals needed to the max. Now as you are both teams you wont get tackled.

So do the trick top of the world (Hold L1+Down on trick stick until your gamebreaker is full) Then shoot as soon as you get into the gamebreaker zone (dont do the beats as this ends the game if you do 3 and score).

Keep doing this until you score the goals needed. You should probably have about 100,000 points, at the end you should get about 5000 skill bills a match. Keep doing this until you have enough to upgrade your player full!