You can have the most expensive make-up, but if you don't have good brushes, then everything falls apart. I think the first thing you should invest in are brushes, then everything else, these are my favorites and they have proven to be excellent.
you just need this dual brush blush
Dual-Ended Blush Brush
this one is all time favorite
Signature Look 12-Piece Face & Eye Brush Set
if you want just to buy one set this is it all you need
Reimagined 34-Piece Brush Roll & Tool
this one is travel size is so cute
Along for the Glide 6-Piece Travel Brush Set
all time favorite
Everyday Essentials Makeup Brush Set with Bonus Miracle Complexion Sponge