How many birds? My suggestions for an easy to manage coop: Walk in. Lots of ventilation. Lots of natural lighting. Outside access nest boxes. 1/2" hardware cloth over all openings including ventilation and windows. Plan on a minimum of 4 s.f. in coop/bird. If you build it with the plan to be able to accommodate a broody hen and chicks, or to divide a section off for addition of chicks or other birds in the future, you will be well ahead of your game, instead of building to accommodate present needs, and then wishing you had more room in the future. Realize that the birds you have in the spring, may not be the same birds you have 3 years from now.
To make it easy to keep clean: Soil floor allows for trouble free deep litter system. You will not have to buy shavings. Just keep adding natural yard debris: leaves, grass clippings, etc. to a perpetual compost system in the coop. Harvest compost as needed for gardening needs. Odor free. You will need to install a skirt around the coop to keep predators from digging into the coop. And you will need to build it such that the bottom framing is off the ground so it doesn't rot. Be sure you place your coop in an area with good drainage. If drainage is lacking, you will need to fix that before you build.
To keep costs down: start collecting hardware and windows, and possibly doors before you start the construction. That way, you can frame it up to take advantage of your free materials. My coop which can be seen in my interview at bottom of signature is styling with free thermopane windows and door picked up at town dump. All other framing should be done with planning to use material with minimum of cuts. For example: If you build a 4 x 8 shed style, you could do floor, back wall and end walls with a minimum of cuts. Hardware can get very expensive. If there's a Habitat for Humanity re-store near you, look for discounted materials there. Typically up to 75% discount.
Finally, look for an already existing building that you could modify to meet your needs. It's amazing what a little paint, a few shingles, addition of a few windows could accomplish with the most basic shed.