I gotta ask first where you are located. Your zone may indicate what plants will do well
What direction does the bed face. Does it get sun all day
If you are not a consistant waterer, consider putting in some kind of irrigation system. For that kind of bed, even soaker hoses on a faucet timer will work.
Make sure that you prepare the soil in the bed before you plant. Add in compost and some fertilizer. Compost will help to loosen the soil and keep it moist longer. After planting mulch the bed to cut down on weeds and hold moisture in.
For plant selection, I suggest a drive around the neighborhood. If you see a plant that you like and a neighbor can grow it you can too.
I would pick long blooming plants that do not require a lot of maintenance.
for a sunny spot and does not need a lot of water once established: Rosemary (makes a great hedge and edible too) has blue flowers in summer. Needs care the first year but can live on little water after it is established. Lavender augustifolia (zone 5-8) Lavender dentata (3 ft mounding shrub blue flowers) and can handle more heat, Indian Hawthorne, Rhapsiolepsis indica, great hedge but you need to start with large plants as is grows very slowly, prune to shape twice a year. Sundrops, yellow flowers in the morning. Reseeds itself, and plumbago. Any of the sages make a good border plant. Low bordering plants could be gaillarda, blue daze, or daisies.
Other plants: penta, geraniums, desert honeysuckle, butterflyweed, echinacea (coneflower), coreopsis, black eyed susan, and daylily.
I would still throw in some annuals like alyssum, marigolds, cosmos, and dianthus pinks for added color.