First my front porch:
Now, when it comes to plants here are some ways to save.
I always check craigslist free section and free cycle, there are always people wanting to thin out their perennials or people re-doing their landscape. Also, check your local library for perennial exchanges. And don't forget to buy perennials that spread and grow. I have divided up my hostas many times.
If you can, invest in a grow light and start seeds indoors, they are very low in cost and are easy to grow. Most annuals can be started from seed, and if you grow annuals let some go to seed in the fall and save the seeds in a paper bag to plant next year.
Some perennials reseed themselves so know your plants