Seed takes time..however you can try all sorts of lettuce, spinach, herbs, mash or rampon in the autumn. I like to seed broadcast in small 1mx1m beds, in succession. This alows a succession of young and old plants and helps keep weeds under control. I simply cut young lettuce with scissors- For most the rest tomatoes, pepèpers, aubergines, squash,brassicas, beetroot, you can grow from plants. Buy and transplant the young plants when they become available in you local market. That is the best time. Watch and follow your neighbour that is the best advice.
Potatoes grow well as do globe artichokes and J. artichokes. There must be others.
Water as necessary.