My biggest suggestions for frugal gardening are:
1) make friends who love gardening and share plants (cuttings, divide and share bulbs, etc.)
2) learn to grow things from seed but also learn how to save the seeds (dry them out, put in baby food jars w/ a label and put in the crisper shelf of the fridge... that's how I do it).
3) make your own compost (something I'm just getting into myself....)
*** I wanted to make a suggestion for those of you who are new to gardening and new to starting seeds.... You are better off watering plants from the bottom rather than watering from the top. My favorite way to do this is to put the container (I like using egg cartons or something that will breakdown in the soil) in a pan or something like that (we use what we call "crawfish platters")... set the plants (in their contianers) in the pan. Then you just poor the water in the pan itself. The plant will suck it up as it needs it and you don't risk damaging the seedlings or little plant sprouts.
Also, my biggest "frugal gardening" suggestion is to be selective about what types of plants you purchase, if you decide to buy them at all. Perinnials (come back each year, in most zones) and bulbs are better investments. They will come back next year and will expand (bulbs multiply). Annuals are pretty and will give you instant color BUT you aren't getting your moneys worth. If you want to plant annuals, do it from seed to keep the cost down.
Just my 2 cents.
God bless,
Julie