What type of soil do you have? To simplify, let's limit it to three choices: sandy/loose, loamy/rich, or clay/rocky/stiff?

My biggest advice is to use your own tree leaves and any lawn clippings that weren't mulched back into the yard to make compost and NOT use things like MicracleGro that add salts to your soil because -- while the initial crop may benefit -- the salts will linger in that soil after the nutrients are absorbed and you won't be able to keep using that soil if you keep adding those chemical fertilizers. You don't have to go crazy about composting. Just pile the leaves together and let it sit. If you have lots of leaves, make your pile a row-shape so it is as long as you want, but no thicker than 3-4 feet. Thicker than that means oxygen can't reach the center.

I learned that from this radio show back when I gardened: https://www.npr.org/podcasts/1087444113/you-bet-your-garden

That guy has all kinds of advice for the serious gardener, too, and I was never serious about it. There are people who actually FLUFF their compost! Can you imagine going out every week or so to toss around dead plant matter with a pitch fork just for aeration? Noooooo! I just let it sit and didn't worry that it would take longer.

If you want to go beyond the pot and have a spot with sun, I recommend trying strawberries. Get live plants and pop them in the ground, then wait until the next spring. They are an easy early crop and they will replenish themselves with runners so you can get years of enjoyment out of them without having to buy more plants. Also, home grown are going to taste a thousand times better than anything in the grocery store. It looks like Maine has already figured out which grow best there. Note some are more disease resistant than others. https://extension.umaine.edu/highmoor/research/strawberry-variety-testing-at-highmoor-farm/

Other easy crops (2 for pots, the rest for ground):

• cherry tomato -- does well in big pots
• rosemary -- extremely pottable! then take it inside for the winter. I'm told this is a winning strategy, but my rosemary always dies in the winter despite coming inside.
• mint -- not just easy to grow, but hard to get rid of once in the groud
• garlic -- my yard is too rocky for garlic, but I grew it for years anyway. It even survived getting mowed down several times.
• leeks -- mine were scraggly, but they made for gorgeous flowers so I let them go to seed and lo! They kept coming back from seed on their own! https://extension.umn.edu/vegetables/growing-leeks
• lettuce -- cold weather crop. Lettuce becomes bitter as it matures, but you can throw seeds on the ground in the early spring and harvest before summer. If you miss the window and it starts to 'bolt' (gets tall), let it go to seed and more will come up next year.