Installation : Choose "expert install", *read what the screen says twice or more*, know about partitioning.
What to use : I just installed one of everything then played around until I found the ones I liked. The other option is to stick with the defaults and get comfortable with them before trying new programs. This way you get accustomed to Linux, then you get accustomed to new window managers rather than having to learn both at once.
Don't be afraid to just take your time, it's better than rushing.