When it comes to plugins, any decent DAW will have enough built in for you to make a pretty decent start and even further – I would just start with what you have – all you need is a couple of instrument patches, an EQ, a compressor, a bitcrusher, a gain plugin and a noise gate and you’re done – and start messing around for a bit..
Mastering is something that you shouldn’t do yourself.. Not because of a lack of talent or anything like that – but simply it is not a good idea to master your own tracks once you have mixed them down.. Mastering is an art in itself and there are people in the world who do literally nothing else.. For now though, just don’t let the master output distort 🙂
I would also recommend checking out http://www.soundonsound.com for some decent tips on how to get the most out of your DAW – they have articles on pretty much all the popular DAWs out there… 🙂
Start off designing your track layout, then your chord structure, then your bass line and build it up from there 🙂
bob6397