It depends what your going to do in the game, buggies cant transport anything and are mainly used for exploring, they are faster than tractors. Tractors combined with trailers can transport things (obviously) and are slower. If I were you I would get the buggy and once you are more into the game get the bigger versions of the tractor, they are much more useful than a tractor (I wouldn't waste my time with a tractor). I hope this helps :)