Agreed. 0.55 is way to heavy.
I would suggest a .45 mono. (a bit of an overkill, but it will help you when you get stuck in the rocks. Use a .40 for your sinker weights. That way you will only loose your sinker, if you get stuck.... or that's the theory. You r line will also be able to take more of a beating. Further suggestion is Double X, as it is nice and limp, with very low memory)
Leader gauge, is all depending on your rod and your eyes. As stated above, if you eyes can handle a .70, then try that. A thicker leader is harder to cast. I use Kingfisher leader line. (be careful when you make your first few casts, as the leader will have some memory from the spool and may be a bit difficult)
ALSO MAKE SURE THAT YOU WIND YOUR LEADER KNOT ON THE OPPOSITE SIDE OF THE SPOOL, TO WHERE YOU USE YOUR THUMB.... or you gonna learn to speak foreign.