There are a lot of different clothes in the FF series and they are easiest recognized from the general FF style. There are a lot of stripes and spots, overalls and lace collars, and the style is very similar in all the clothes. Besides the clothes on the FF creatures, there have also been separate clothing sets for sale.
Some other series have very similar style of clothing as the FF line, such as Tierwelt. They have almost exactly the same patterns, but luckily Tierwelt line clothes are bigger than the FF clothes so that's how you can identify them.
It can seem difficult to know which sets are exactly right for a certain animal because there are so many different kinds of clothing combinations even in the same animal species. Sometimes two packages can look exactly the same and include the same family, but still the clothes are different. Some animal families were only published with the same outfit every time, but most animals have worn different clothing sets depending on the release. The best way to pick correct clothing combinations is to check pictures of families in unopened packages for the clothing sets. The Forest Connection has a lot of information on the different clothing sets.