Certain annuals and bulbs are surefire ways to help pollinators, assist crop growth, deter or distract pests, and help mitigate diseases from hitting your crop. Here are a few of the best annuals (and one bulb) to basically pair with anything to help it out:

Nasturtium, borage, calendula: these are the all stars of companion planting - they attract all the aphids away from your crops and can take their attack, they are some of the best for pollinators, easy to grow, they don't have a bad pairing I've ever heard of, and they're even edible in a pinch. Chuck them in with basically any crop and they will help.

Cosmos, sunflowers: not as amazing as the triumvirate above, but they help attract pollinators very well, do attract away some aphid attention, are easy to grow, and the sunflower stalks can even help as stakes for some climbing plants to go up. They shouldn't hurt to add in where there is room.

Now for the bulb: the onion, and all its relatives (chives, garlic etc). Amazing at repelling pests and diseases, masks the scent of vulnerable plants so they hide from pests, like carrots from carrot fly. Word of caution however, do not plant them with any legumes, the onions secrete something that impedes their growth.

Obviously companion planting is a huge topic, but these are some surefire easy ways to implement it. If you don't have a plot or veg then chuck them in anyway: they help flowers and ornamentals just as well!