Half rounds at the bottom or scaffold poles should work. I've got a single electric wire 10cm up around three sides of the pen and a single line of barbed wire on the forth, that was to avoid the 'won't cross the electric wire' syndrome and it is where the water is. Both work well. The electric is no big deal, they learn to respect it in minutes. Prior to putting up the electric wire/ barbed wire they were having a good old dig under so something is needed. For the gate, just ensure the two hinges are pointing in different directions so they can't push it up.