The first thing to do before getting started with changing up the decor is to have a plan. Do you want to change up your outdoor space completely or just make minor changes? 

Before buying furniture, make sure to do a deep cleaning of the space. This will help you to get an idea of the potential the space has. A nice suggestion would be to hang bamboo screening and center a focal point over it.

This focal point can be a medallion or showpiece plant. Add a vintage side table or some type of shelving. This will be helpful for get-togethers, so guests have a place to set their drinks down. The best use of lighting is to start in corners. This will add depth. If you do decide to purchase string lights, try to get solar-powered ones. These are often inexpensive, and you can utilize command strips to hang them. These special double stick tabs will prevent damaging outdoor walls with drill holes. It is also possible to find solar-powered light-up garden decor. These are often relatively affordable.
You could have beach towels and decorative pillows readily available and use neutrals for more of a spa feel.  

For privacy, hang a tapestry on a shower rod. This is essentially a makeshift curtain. You could also use bamboo shades as opposed to tapestry. Another affordable way to spruce things up is to utilize planters.

If you do not like the planters you already have or found at local yard sales, you can always paint them or change them to your liking. Be sure to utilize some type of coating or special outdoor paint to protect them from outdoor elements.

If you want to get creative, you could try a pallet vertical garden. This can be accomplished by utilizing black fabric that eliminates weeds as a base and building up from there.

For an enjoyable summer outdoor setting decorate an intimate sitting area using a privacy screen. Utilize plants and lighting for depth and warmth. Add some refaced used or new outdoor furniture. Enjoy entertaining your family and friends in this new summer atmosphere.