It is hard to work out, especially since they stock the clothes seasonally like adult clothes. So if you want winter gear, you need to start looking late summer/autumn. Got stuck once trying to get some tracksuit pants in the middle of winter, ended up having to look on ebay, as the spring/summer stock was already out. Have certainly made some bad purchases estimating sizes and seasons.

All you can really do it buy small amounts of different types and see what works, then go out shopping and hope they are stocking what you need. There were some outfits I really hated and others I got a lot of use out of.