I think frugality comes as much in using the appropriate product - and thus wasting neither time nor money - as from being thrifty so, for example, I do spray our weedy paths and boundaries with a glyphosate based product as it works out cheaper, quicker and less smelly than gallons of white vinegar. I use no other garden chemicals.
I also always buy in fresh seed sowing compost and and fresh planting compost for tubs, baskets, window boxes etc as it gives best results and reduces disease. However, I recycle old compost as a soil conditioner or mulch on the garden.
We have a "compost corner" in the kitchen for all waste which can go on the compost heaps - fruit and veg trimmings, egg shells, coffee grounds etc and also compost the grass after lawn mowing, weeds after they've been pulled and left to dry for a day or so, cardboard and so on. I've been much better at collecting seeds from my favourite garden perennials this year and taking cuttings form plants I've pruned to use as spares, swaps or give away.
Sowing seeds for the veggie plot is generally cheaper than buying plugs but I still buy plugs of most salad leaves as it saves me time and space for seeds of more unusual veg I can't buy. Similarly, we grow soft fruits which are easy to grow but cost a fortune for a small punnet in shops.