I can have a complete description for the trophies:
The Artsies trophy is located in the Bayou, From the house, you go right into the next screen, past the fly trap, cross the bridge, go south-west and cross another bridge. You can get it when you see two fly traps and you go past them like so.
The Nerdie Trophy is located in the carnival. Follow the main road into the carnival area and go straight. Go straight onto the footpath and go until you hit the fence. The big tree on your right has the trophy
The Richies Trophy is located in the Mega Mall. Go upstairs and go past the electronics dealer. It is between the computer and the utilities heaters.
The Streeties Trophy is located in the graveyard. When you go back from the Bayou back to the city, you will go past a graveyard before you can leave it. The closest one to the exit back down will be the grave to look for.
To get 10 rep points and the clubhouse keys:
1 - Get 50 Relationship Points with one member
2 - Get 50 Relationship Points with two members
3 - Get 50 Relationship Points with three members
4 - Get 50 Relationship Points with all the members
5 - Get 100 Relationship Points with the leader
6 - Move to a place desirable to the group
7 - Get -5 Relationship with the rival group
8 - Max out the certain skill
9 - Finish the Rep Mission
10 - Give the group trophy to the group leader