FIFA 10

This will also unlock the achievement for winning a game with 100 chemistry:
Perfect Chemistry - 15G

This is alot easier than first thought and is alot easier than 100 chemistry from different nations.
Firstly go to Squad and Press Y which will bring up team options, here select Squad Selector and Create a New Squad.
You will then be asked to name it and then will have a blank 4-4-2 formation on your screen.
Now go to Search in the menu and define your search:
Level - Bronze
League - Coca Cola League 1
Max Buy Out Bid - 200
Now when you search, buy out players for 200 coins and add them straight into your team (Assign Now and pressing Y).
When buying the players write down on a piece of paper the positions you have got and THE TEAM THEY PLAY FOR. ensure that they all play for different teams as this is what the achievement asks for. So you may have a RM from Millwall and a ST from Huddersfield.
Once you have got your starting 11, you will need to buy another 7 too put on your bench. Some of these CAN be from the same club as those in your starting 11, however if you want to be safe you can have different clubs but dont need to be in the same league (chemistry isnt effected by the bench).
Then go back to your squad and put all the players in the correct positions .. at the end of this your chemistry should be around 93.
Finally you need to search for a Silver manager, you should be able to get S.Mclaren, J.Gannon for about 200 - 250 coins buy it now.
Add him to your team and hopefully (fingers crossed) your chemistry should be 100.
Then all your need to do is play a single player match.

! DONT PLAY A TOURNMENT MATCH or it will NOT count !

Set the difficulty to Amatuer and 4 minute half. Once you win the game the achievement will pop up.

Note:
Cost of doing this
18 players X 200 coins = 3600 coins
1 manager X 250 coins = 250 coins
TOTAL = 3850 coins
Getting coins can be achieved by selling cards and/or winning matches.

I would suggest trying to get Perfect Chemistry first then this one will be a breeze.
Once you have a 100% chem team, right down the players and there respective clubs, posistion, and formation. Now where you have players from the same club try to replace them.
Use the seach tool in the trading section. fill in his posistion and formation and if possible his nationality. See whats avaliable for cheap (bronze cards will do just fine) Ensure you try to keep your new player as close to the old one as possible to avoid losing chemistry. once your starting 11 are all from a different clubs and you still have 100% chem. play a match online or offline and you must win.
Note tournament games do not unlock this acheivement.

i have a team for this send me a message and give u this team and give this soulution a + it helps when people are from same league and country by the way 4-4-2 is the formation here are the palers i got
Manger -GOLD-R.BENITEZ

ST Left-GOLD-(Lucarelli)-Club Napoli Serie A- 4-4-2 ITaly

ST Right Gold(-UcHE)-Club Real Zaragoza Liga BBVA Nigeria 442

Lw but plays LM GOLD (Langella )club Bari Serie A 3-4-3 Italy

CM GOLD(PinZI)Club Cheievo Verona serie A 4-4-2 Italy

then ST who plays CM (David Barral) Real Sportiong Liga BBVa formation 3-4-1-2 Spain

RM Gold (Valdo) BClub Malaga cf Liga BBVA formation 3_4_2_1 Spain

LB Silver (Stewart) club sheffield utf co cola champship 4-4-2 england

CB Silver (javier Baraja) Club Real Valladolid Liga BBVA 4-4-2 Spain

GK Gold (Pinto) Club Barcelona 4-4-2 Spain

CB Bronze (OLMO) Club Elche cf liga adelante 4-4-2 Spain

RB Gold (Javi Venta)Club Vilareal CF Liga BBVA 4-4-2 Spain

HOPEFULLY THIS HELPS!!!!!!!!!