What is the best trailer for my Subaru Outback station wagon?”
Most hardware stores such as home depot etc have a good selection of utility trailers available. These are generally quality trailers which are easily registered etc. If you go with something homemade, it is probably going to be heavier which will limit your cargo capacity somewhat, and it is going to need inspections etc before it can be registered. A trailer purchased from a well known manufacturer is also likely to come with a warranty, and will be more easily insurable which will protect you and your property.