All of my coasters are rubbish at the moment can anybody help?

Ask Alex Wohlbruck, he's a pro.

Just use Moby's custom supports, a set for footers, a set for catwalks, a set for brakes, a set for connectors, some tree sets, sets for building buildings, and any other sets you can find. I nearly download any piece of CS I find and use it for my coasters and parks. :P

You forgot a multitude of sets for scenery.

Those are both great responses. I would add that it also takes time to get it to look just right - about half the time spent learning where the stuff is in each custom set and the other half selecting the correct items and placing them effectively with your coaster/park.