fc2 apt repositories

[Advent Systems]

Hi Guys,
       After checking a bunch of sites I'm more confused.  When I setup 
apt-get It asked me to pick some repositories and mirrors.  There were 
about 20 or so.  I just picked the top 4 from each category.  Was I 
supposed to select them all?  I hear about some software I'd like to try 
out (like pixiplus) but it's never available in the repositories I 
selected.  I have downloaded and installed a few rpms that I "had" to 
have but from what I understand your not supposed to "mix" like that and 
I'm wondering If I'm screwing my system up little by little.  Whats the 
best way to setup/run apt-get?  I'm running FC2 w/Gnome.

Everything is working fine, or so I think.

Thanks,
Bob Randal