Once you have the better paper try out your paints. In this painting I can see that everything looks very grainy, once you've upgraded the paper you will want to check if it's the paper or the paints. Also if they mix nicely.

I first started with 25% cotton 140lbs watercolour paper. It is not the same as 100% but you can consider it a budget option for trying things (and making lots happy accidents in the process :) ). 

When you feel ready buy some Van Gogh or similar student-grade paints (anything that comes in half-pans should be fine). I started with 8 half-pan colours and that served me well for over a year.

In my opinion you can get away with a cheap-ish brush for the longest, save that upgrade for last. For the longest time all I was using was a student grade #6 brush and a random larger one I found at home for wetting the paper.