Particularly with warm season crops like tomato plants you don't want to mulch with anything, as it keeps the soil cooler. Here you want to get the plot to be as warm as possible, including the soil. If you want to reduce weed infestation of the pathways around the beds, use whatever you are comfortable with. Having a bulk load delivered is cheaper than buying by the bag (at full price), but you only want to get a load if you need a sufficient quantity.

If you have the time you might watch Craigslist or Seattle Freecycle. You can post requests on Freecycle too.

Every Fall, I collect maple leaves and let them compost with coffee grounds and whatever else I can find. I don't use neighborhood lawn clippings as I don't want pesticides. I think the issues of using wood bark or chips on a vegetable garden are due to the tying up of nitrogen and maybe attracting sowbugs.

Absolutely free & a good source of nitrogen is your own herbicide free grass clippings, but if you don't have a lawn maybe you can ask a friend to call you when they're going to mow & you can go pick up immediately. It's important to dry them right away. When I've bagged up for a day or so before drying it was harder to dry because the matted together. Also shorter clippings dry faster because the separate easier.

This is how I do it:

Mow on a dry day, spread out on a tarp to dry, then use to mulch your vegetable garden. I prefer to spread a light 1/2" layer and build up to about an inch around greens & more around larger plants. When you put them in a bucket & spread by the pinch it is done rather quickly because they're loose & easy to move around with your fingers without damaging plants. Don't bother with a tool.

Free used coffee grounds from coffee shops also work well when topped with dried grass clippings. The grass prevents splashing up of coffee grounds onto vegetables and evens out the mulch for a neater appearance.

If you have access to free straw or old hay either works fine for larger plants like cucumbers & tomatoes. I mulch tomatoes because I don't want weeds growing or the soil drying out. I haven't considered that it kept the soil cooler. I gather about 3 straw bales in the fall & leave out in the rain on an unplanted part of the garden until the next late spring when I start mulching strawberries & larger plants again.

For a smallish veggie garden, I'd look at the plastic sheet mulches. Reusable, excellent at keeping weeds under control and depending on color used, can significantly increase productivity. And are no more expensive than purchasing a bagged mulch. Red plastic mulches are highly rated for hot season crops like tomatoes, peppers, eggplants, cukes or melons but they also come in black, blue, green or brown. And in silver, which is designed to keep insects at bay.

Very easy to use if applied in conjunction with drip irrigation or even soaker hoses.