Get a brake.

After that, pretend you haven't read anything about others' experience with the bike, then decide based on your experience what needs upgrading. You'll get a lot of advice about what "needs" to be replaced, but unless you feel the need firsthand, you could be wasting what sounds like precious cash. You'll be kicking yourself if you splurge on a non-critical upgrade, and then something else blows out and you can't afford to replace it.