First question is what are you planning to do? Is this for a home lan w/ no internet connection? If so, keep it simple since you're a newbie and just make a / and a /home partition. YMMV
Otherwise, I would suggest a /boot partition ~40-50Mb, /var partition ~100Mb, more if storing mail for multiple users, /home partition so you can reformat/re-install without losing your stuff, usually I make this as big as possible on the server, then export it using NFS and samba to any clients, a /usr/local partition for stuff you compile yourself ~500+ Mb, and the rest on /.
Everyone has their own philosophy for partitioning, so you'll get different answers. Back in the day, I just learned through trial and error on partition sizes, and just found what I was comfortable with. You'll do the same.