So perhaps this should be obvious, but what does it mean when the name of a crop is highlighted in red for a plot? Also, about how many plots/size of plots should be neccessary per dwarf?
Red writing indicates that you can't plant that crop at that time; sweet pods can't be planted late in the summer, quarry bushes are forbidden in late autumn, and nothing can be planted late in the winter.
As for size of plot, that depends significantly on other factors. Judging by what you've said, your fortress is new and fairly small, so 5x5 should be more than adequate, especially if you cook the alcohol into prepared meals. I'm running a 200-dwarf fort on the equivalent of a 6x6 plot and have room to spend on fiber and dye crops.
Edit: Just as a f'rinstance, a 2x3 plot, intelligently set up to maximize food output, can grow sweet pods or quarry bushes for spring and summer, quarry bushes in autumn, and plump helmets in winter. Leaving aside the plump helmets, the sweet pods and quarry bushes would produce, over those 9 months of growing, 6 crops per tile. If we assume an average size of 3 plants in a harvested stack, this leaves us with 6x6x3 plants harvested, or 108 plants. Since sweet pods can process into 5 units of dwarven syrup per plant, and quarry bushes process into 5 leaves, we can have 540 units of cookable food, which will become 540 +quarry bush leaf roast+, and make the dwarves much happier than raw plump helmets. Make another plot for brewable plants, and you should be able to support up to 75 dwarves before you need to expand your operation.