Unless you are going to teaching in a school with a high percentage of EAL, behaviour is the most likely to be useful. However, on that note also read everything Tom Bennett of the TES has written www.tes.co.uk/article.aspx?storyCode=6175180
I don't know what philosophy covers. Is it philosophy in the classroom or educational philosophy.
Teaching outdoors does sound fun, but unlikely to actually happen due to lack of space, poor weather, resources etc.
Maths is also a subject that is very different to other subjects to teach. Very little writing, discussion, giving opinions. Because of this, most general INSET is simply useless for maths teachers (indeed some schools do separate maths INSET instead of requiring maths teachers to sit through stuff irrelevant to them). So when you make your decision, think carefully about whether it's something you are going to find useful, or whether you'll be sat listening to a load of stuff about essay-writing or circle time wondering when you can get back to the stack of work you need to do.