110% of the time recommend thrifting. It's fun, it's cheap, it's awesome.
I suggest making a list of basics pieces you'd want to style with that way you know what you're looking for rather than being overwhelmed with the amount of variety at a 2nd hand store. Based a quick google of Coquette Aesthetics I think you'll be able to find a lot of the button ups and basic/base pieces you'd want. That way when you spend more money and buy something new it can really be a statement piece.
Happy dressing!
-SN
p.s. don't be afraid to shop in the sections outside the size ranges and gender categories, sometimes things get misplaced or you find a piece that can be easily taken in a little