Thats good (although it must have played oddly to a left hander given the camber of the bridge and fingerboard!) For RnR/rockabilly, assuming you are wanting to learn to slap and pizz (rather than arco) then I would concur that Innovation strings are the best value solution. Silver Slaps (or their yellow-coloured cousin Golden Slaps) are gut-alike strings that have very easy low tension and are much cheaper than steels (which would in any case hurt to slap). An alternative would be Presto Nylonwound Lights (from Thomann in Germany) which I personally prefer, but there's not much in it. There are more expensive alternatives (Velvets, real gut strings etc) but I wouldn't even think about those yet.