For chain, get a DID VX X-ring chain, very good value for money, excellent chains and because it's X-ring it will last longer (obviously if you take care of it well.) For sprockets, get a good front, like a Renthal or JT Sprockets one if you can, the front wears faster than the rear. On the rear any steel sprocket will do, don't bother with aluminium ones, they don't last as long and the weight saving is not worth it for a road bike. Again, Renthal or JT Sprockets are good brands, but there are plenty of other decent brands out there. Nowadays most sprocket companies have a fairly good standard so you don't need to worry too much about which sprockets you buy (those are just my preferred ones.)
For brake pads there's only one real option and that's EBC HH pads. They cost a little more, but they last much much longer so in the long run they will save you a lot. They are also the best pads in terms of stopping power that I've used so far and get the thumbs up from a lot of other people on here.
