I have been in this hobby now for 10 months. I started with a filter pad and bio balls. Since then I have switched to the sock and put rock rubble and have been super happy with the results. I was getting nitrates with bio balls. As for a sump the bigger you can go the better. Basically measure the area below where you are putting your sump and get one just a hair smaller. And I don't know if you want a new one or used but there are a few guys here that can make you a sump and there are plenty others that are selling good used sumps. I picked mine up used and it does its job and looks amazing. And as other have said NEVER trust everything your lfs (local fish store) tells you.
Oh and btw when you do get up and running please do not buy damsels the get you cycle started. They are a pain in the *** to remove and the are extremely mean when they get a few months old.
Switched over to the dark side of lighting. LEDs. The force is strong with this one!