If you are coming in the next month and staying for a few months, you should bring kites in between 7-12 square meter.
You do not need wet suit in Sep. You can use a shorty in Oct and Nov. After Dec. a full wet suit is necessary.
People who live in Taipeikites at different spots depending on wind direction. I live in Penghu, 1 hour flight away from Taipei. It is always windy here after Oct.
A few useful links are listed here:http://www.penghuwindsurf.idv.tw/https://www.facebook.com/groups/113320695399169/https://www.facebook.com/groups/389888624381801/