Depends where you are and what your growing but now is a good time to start a lot of winter veg for growing outdoors. I would stick to salad greens if you are new to growing and hydroponics. It's easy and will save you the most money.
Discussion
I'm 100% growing salad green but since I'm not totally new to growing stuff at home I was thinking on growing something "fancier" too (maybe some cucumbers or some zucchini no start)
That really depends where you or how much extra effort you want to put in to making the plants grow then. We don't get a lot of light here in the winter I tried overwintering a tomato here a few times it survived but didn't look very happy at the end of winter so I doubt producing a cucumber without supplemental heat and light here would work at all here.
Hear shouldn't be much of a problem for me but light definitely is. The plan is to set some led lights with a timer to get 12/12 cycles until they start flowering, then change to 14/10 cycles