Tomatoes - roses and geraniums - all like coffeegrounds. I save my coffeegrounds just for them.
Had to laugh at the notion that dirt is for free - doesn't do you much good if it is basically sand as in practically white beach sand and huge rocks with ancient shells and critters embedded. Even found one that looked like a dino head. So no, if I want to grow something in my garden I either have to seriously prepare a bed or grow in containers.
Sweet potatoes are about the only thing that does fine on it's own.
Find out what grows best locally in your own area and start with that. You can always experiment along the way, I try something new every year just for fun.
My tip, find garden friends and seed swap with them, I regularly exchange plants, seedlings and seeds with my garden friends. Going over to pick up a nice palm for free - cha ching - saved $12.98 over buying at Lowes garden center.
Lowes garden center - has a clearance section and I regularly pick up plants there for half price or less - skip that idea, if you don't have the time it takes to make them happy and healthy again.
Recycle your bottles as garden path borders, built a cool outdoor bar from pallets and paint it with leftover paint (one of my garden friends did this) - I'm no carpenter, so my projects involve mosaic stepping stones and glass and mosaic garden art. It's fun, unique and a cheap, creative outlet that is environment friendly.
My next experiment will be growing coffee (three bushes if I can finally get them) and a pineapple grown from the cut off top of the fruit. The coolest thing I ever found was a guy at the local market that had a variety of Macadamia nut tree you can grow in Florida (just a propagated branch)- who knew? Looking forward to my first crop this year - and incidentally - it also likes coffee grounds.
Don't forget to grow something for the honey bees and the butterflies. One kind of butterfly always decimates my parsley and the gentle honey bees are crazy about the red blooming pineapple sage (salvia) and go gaga over the African Blue Basil (get it at Lowes it is a peppery, slightly spicy Basil - awesome flavor - just don't cook it, add it the last 30 seconds before the dish is ready.
Googled the pineapple sage because the leaves smelled so nice - yes, it is edible and you can use it for tea - planning to try it with my orange mint as I like my spearmint just the way it is.
Our big avocado tree always makes baby trees every year - I think this year I might see about selling them. Mr. R. takes sacks full in to work and they disappear within minutes. Organic avocado - yum.
My favorite thing to grow, because it is so easy are herbs - free tea:), if you haven't smelled and tasted fresh lemon verbena (sweet lemon) you don't know what you are missing. Although my Puerto Rican mint bush is giving it a run for it's money - not quite as intense, but a fresh, light and sweet mint flavor. Free seasonings, like rosemary and bay leaf and you can concoct your own Italian and French seasoning mixtures in a flash. Free medicine even if you are so inclined and study up a little.
Although I must say I've never tried growing ginger even when it sprouted in my kitchen - next time:)