Like everything cooking is practice, the more you do it, the better and quicker you get. I can knock up even quite a complex meal quickly now. We have our favourites that i can now cook of by heart. New recipes i follow the instructions the first time, then start tweaking it once we have tasted it.
Mostly you can add what you like to recipes and make them to suit you. there is a lot of recipes that are actually meat dishes, that i turn into a veggie option ( with Quorn)
My meal plan takes me about an hour on a sunday ( shopping day is Monday) i look through the cookbooks and previous weeks plans. see what takes my fancy, and what fits into my week with work etc. and what stuff we have in fridge/freezer/cupboards already and go from there