Again, i will go back on topic, but it is not off topic to talk about how to get good armor to kill chammy. Sorry, but it is true, anyway.
As far as killing Chammy, i would acctually not do it first. IF you can kill the Lunastra, do it first to get the Sabre, then use that on chammy. If you cannot yet kill Luna, then just do as ive said b4, Practice, Practice, Practice. If you want a tetimonial, i just kept doing Green Congadrome and over time i got better and better till i killed it, like me, so far i have killed 5 green congadromes since my first kill 3 days ago, lol.
If you still have trouble do what i do, run out and find openings, exploit thoes openings. If you die after only 5-10 mins, just abandon and try again.
I know you already can do it, just slow down, find the openings and do it.
I have faith in you Young Grasshoppah.