This really is a wonderful community of gardeners! I've learned so much from talking to other gardeners, or sometimes just reading. I have a feeling you are going to have a lot to offer by way of gardening in no time.
You definitely should grow nasturtiums! They are great companions for melons and broccoli too! Broccoli likes calcium, nasturtiums don't need so much and it will deter the beetles and other bugs. Grow it right under the broccoli and melons, that way when the sun gets hot, they will also protect the nasturtium from the hot sun.
Marigolds are another good choice. They are really good at repelling pests but they will attract lots of butterflies.
Herbs - basil, rosemary, sage, oregano.
Nasturtiums - the flowers and leaves are edible and often used in salads. The flowers are milder in flavor than the leaves.
Marigolds are easy to grow and great companions in the garden.
