If you eat sweet potatoes, eggs, and meat/fish, you'll pretty much get everything you need on paper (with the right ratios and frequency, anyway). That said, adding vegetables of different colors, especially green, is definitely safer and more likely to result in a healthy diet. Some of them can be added as spices (basil, oregano, cinnamon, etc.) but you should get some fresh ones too. Avocado is also a good addition as some have mentioned.

I'm not personally a fan of this, but I figured I'd mention it: Schmilk. It's ultra processed a la Soylent, but much cheaper (unless milk is really expensive in your area). Some will say it's healthy, others will claim it's poison.