I started off with store lambs in winter and had a good few months to decide if I like them and put them to the tup in the following autumn. And it is good to get used to them (and all the husbandry tasks that sound awfully complicated... like foot trimming, shearing etc) before you get a tup on them
I personally would not put ewe lambs to the tup, it is just not worth it if you only have a small flock. Better to let them grow up. Also they don't need much feed in their first winter, just hay if snow/hard frost and quite small amounts of feed (sugarbeet is good too) when snow/v cold for a few days (if there is decent grass in the field and not overstocked).