Starting out with everything at once may indeed be very challenging! If you aren't going to be too disappointed by learning a whole lot your first year, more power to you! Go for it all at once!
But since garden "learning" usually involves some lost crops, you might prefer to learn a little bit each of the next 2-3 years, and start out with just a few crops your first year. Maybe Improve your soil and find techniques that work for you, before starting 20 different crops all at the same time, for the first time ever on all 20.
When I was disappointed by having 80% of five trays of seedlings all die on me, a more experienced gardener assured me that every gardener has to kill a certain number of plants, and it only means that you are still learning ... and we ALL are still learning, even after decades of growing.
Or maybe you're smart: buy a few cells of whatever is in season, stick them in the ground and see what survives. You'll learn fast which ones need something they aren't getting, and specific advice will stick when a dozen plants go from yellow and wilting to green and booming overnight!
If advice varies, remember that everyone does it "their way", and most ways can be made to work in one climate or another. What is easy for one person may be hard for another.
Pick whatever method sounds easiest to you, try that, and if it works, keep doing that. Only pursue the harder methods if you need to.
>> semi prepared 8 by 8 foot garden.
Opinions differ, but if your soil is not-very-good, it might be a candidate for "rows" instead of "intensive" or "square foot" spacing. If the soil is not fertile, roots might want want the extra space to wander through, in order to find enough nutrients and water for the plants. But then you have to weed the rows that you walk in!
Consider re-making your bed from 8x8 into 4x16 or even 3x20'. Then you won't need to walk on the soil as you sow, weed and harvest. Walking on the soil compresses it and squeezes out the air spaces that kept it well-ventilated and well-draining.
Or leave it as a rectangle, but run 1-2 paths through it that divide it into 2-3 narrow beds each 3-4 feet wide. Then yo8 canr each the whole bed while never walking on the soil.
Tall things and anything that grows on a pole or trellis or string should go along the North edge so it's shadow does not shade other plants much.
Advanced gardeners plan so that early spring rows like lettuce, broccoli and Bok Choy are harvested and pulled out in time for summer crops like beans, eggplant, peppers (no tomatoes?) and maybe okra. And they think about what crops will be done in time to be pulled and make room for a Summer/Fall crop of Chinese cabbage, Bok Choy,or whatever.
It is smart to plant together things that want the same amount of water and fertilizer.
>> Please do an article on how much water each plant needs also
Too much work for me! All I know is that Brassicas like Bok Choy, broccoli and cabage like "uniformly moist" soil. I THINK that lettuce and all kinds of peas like the same thing.
I'm not very experienced yet, but here's my rule of thumb:
If you stick a finger down 2 inches into the soil, that should still be slightly moist when you water again, for plants that want constant water. A drought-tolerant plant that like well-drained soil might go dry as deep as 3-4 inches between waterings, but I'm sissy and try not to reach that point. .
