Definitely kitchen & baths!
Of course, there are always small things that make a big difference... when "big" things are in good condition and fully functional! I always caution my Sellers about using their improvement budgets smartly.
That means: put your money where the water is first! Big ticket items, like Kitchen and Bath, must be functional, clean and attractive in order to be liked and sell well. If there is now instant money available for it it is best to plan ahead, refinance/borrow if you have to for the necessary improvements, otherwise no amount of small things will give you a real good payback. Houses tin need of kitchen and baths updates are harder to sell and so there is a natural loss of value caused by limiting your prospective buyers pool, increasing time on market, carrying costs, etc.
so... once your big ticket items are taken care of you can clean up the landscape, fix up the driveway, clean up the house, de-clutter, paint, lightly decorate, reconfigure if you have to - in that priority - to get the most for your improvements.
Good luck! And don't forget to be sensible about the products you use. The "greener" they are, the better you are on the environment, home value, your health and, eventually, your pocket :)