Best Carnifex advice I can give.... Do a search for a magnetized Carnifex (or magna-fex, or other permutations.) It is using small powerful magnets to make it easy to modify your fex as you like.
Also, you really need to get the Codex, it will give you information you need to make modeling decisions.
What type/ how many fexes you use probably shouldn't be your first decision, for it depends on the rest of your army. I recommend you get the codex, do some web reading, and figure out a 1850-2000 pt army you think you will eventually want.
Then post it and ask for critiques. Take the critiques you want to (not all of them), and redesign the army. Then figure out lower point versions 1500, 1000, 750, 400 (whatever), and build up to them.
Good Luck
Lictors: You get some heated discussions. Worthless, Only One Ever, Go Three or Not at All, and Don't Leave Home Without'em.
The tricky part about Lictors is that they *seem* amazingly awesome, so folks use them against the wrong targets. Then they get toasted...
I run one, it gives me a bit of 'pop' that I can put to threaten, or assist, or maybe take out a small squad. I am almost always glad I took it, except the game that I forgot to bring it in.
But running 2-3 can do great things against vehicles of most types. And they work great with assaulting gaunts. (When you get the codex, look up Feeder Tendrils)