mate I suggest you start off just by reading through the posts on this forum, seeing what other people are using and what they rate / hate when it comes to software....there is so much going on it would be impossible to tell you where to start, it all depends on your own taste and what you want from any piece of software...
have a browse round here, www.bangingtunes.com has a good production forum, read some copies of Future Music mag or Computer Music ( www.futuremusic.co.uk) .. just read all you can mate then go ahead and get stuck in!!