Lambs will go through the wire fence (no matter how docile the breed you choose), yes, so I would get that section patched with stock fence or a few hurdles or something.
If you start with 2 shearling ewes and 2 ewe lambs, you will need to be able to keep them separate when tupping time comes. If your plan is to send the 2 shearlings away to a tup, then that's fine, but if you are bringing a tup to your own spot and don't want to tup the lambs, then you will need another paddock to put them in.
Sheep are lovely and great fun, but they can be a bit keen on dying, and do need pals of their own species. So if you are not planning on tupping the lambs, I'd get 3 ewes and 3 lambs at least, so that you've a fighting chance of still having at least a pair of each when you need to keep them separate at tupping time.

There is also an argument of starting out with experienced ewes, so that when lambing time comes around, at least one of you knows what they are doing!

So some people start by buying ewes with lambs at foot. (And if a few of the lambs are males, that means you'll have your own lamb to eat sooner

)