Lots of good ideas here, and I especially concur with deep mulch for improving soil. It takes a few years, but it will happen. Once the soil is healthier, many things will reseed. In my garden that includes dill, cilantro, Malabar spinach, cherry tomatoes, amaranth for both leaves and seed, buckwheat, arugula, Japanese red mustard, lots and lots of different flowers.
Building raised beds: untreated lumber from dumpsters, craigslist and FB marketplace.
Containers: Home Depot and Lowe's have empty pots that get returned to the grower for recycling. But you can take anything as long as you don't make a mess. Just look around in the garden center for tall carts with empty pots, usually near the back. I have little pots and trays to fit that I have been using for a few years. I also have a collection of tree-size pots that I use for growing sweet potatoes. They eventually degrade in the sun so I have to keep them covered when not in use.
Filling raised beds: start in the late fall so it has time to age, plants don't like fresh wood chips or sawdust. Sometimes you also just have to buy soil.
Plants and seeds: My local free produce market often gives away seeds and plants in the spring. It's run by Bountiful Cities, local to Asheville but other cities may have similar. I've also seen free seeds at another local garden.
Weeds: Eat 'em. Dean Green has a website, probably a book also, called Eat The Weeds. When you pull weeds, just shake off the dirt and let it lay on the ground it came from. Exception would be if it has seeds, then dispose of it further off. I don't put seedy weeds in my compost because I can't be sure it will get hot enough to kill the seeds.
Drought: Every fall, we haul home a couple trailer loads of bagged leaves from local neighborhoods. Most are in paper bags so another bonus for compost. Rule of thumb: soil never wants to be naked. Cover it up with dead leaves and keep it covered. It really will help keep the soil moist and cool when there is no rain.
Scrounging: Don't be shy! If it's laying on the curb, you're doing someone a favor if you pick it up. There's a limit, of course. I can hear my husband saying "Amen" to that.
A quick word about potatoes. I know they are cheap in the store, but they can go in the soil earlier than many summer veggies like tomatoes. You can let other things grow around them and since the potatoes are shallow, you can harvest with a minimum of disturbance to other plants that want to stay longer.