What can I use to give my cement patio a nice look with little cost?

Shop your house first! A rug or pillows or any suitable decor that can be repurposed? Start there, then add in items from Goodwill, flea markets, garage sales, thrift shops before hitting the discount retail shops.

I painted mine with a roller; one color (tan). Let dry. Use masking tape to create grid pattern of 2'x2' squares. Sponge on burgundy paint, sponger the squares around the edges, gradually fading lightly into the center. All to dry. Remove tape and the result is "terra cotta tiles". The tan grid lines look like grout. I also used a sealant so it lasted longer.

Rustoleum has a spray paint that is "frosted" glass. Let's the light in, but provides privacy. You can with with or without a stencil.

Find some stencils on Amazon. They can make a boring patio look very different.

The most inexpensive way is to use a colorful outdoor carpet.Then make some container plantings around.

Think of the slab as a floor in your house. After you place your key patio furniture pieces, find an outdoor rug(s) that complement them and then add a couple of complementary accessories to complete the look. A cement slab is a nice neutral base - work with it.

If you have lots of energy you can paint it.