Carcassonne Central

I have never done any thing like this before, what should I know before I start? what should I know to avoid problems or mistakes.

Which expansion should I start with?
I would love to try an expansion that helps reduce the need for palyers to push so hard to farm.

I would suggest Mountains, one of the many Forest expansions, or some of the River expansions/variants.  Each utilize different methods of gameplay that don't push for farming. 

• Forest adds hunters/rangers as follower types, and the tiles are played (& features completed) in much the same manner as cities.  Ergo, no long wait until the end of the game for scoring, like with farmers.
• The River expansions/variants add fishermen as a follower type.  As a variant, it can be used if you already have The River and/or The River 2, but the expansions add a whole bunch of rivers, lakes, and streams to the Carcassonne countryside.  The tile-laying and scoring method are much like the existing roads, which again means no long wait for the endgame.
• The Mountains expansion offers an entirely unique scoring method based on tile placement rather than followers (although, you can always invent a Variant for your own use that would allow for the deployment of Miners as followers).

 
One thing I would suggest is to have an idea of what materials you intend to use, and how feasible they might be when used side-by-side with the official tiles.  There are many different types of suitable materials out there - I took advantage of an ordering mishap at work and brought home a dozen cardboard shipping/packing boxes.  The surface holds my label sheets well, and the thick cardboard makes for a very sturdy tile.