Welcome to the forums.
Banderbe is right in that you could easily spend more than $200 to convert to the ideal system. For the time being, though, let's assume that you want to stick to your budget.
Basic necessities: Lighting, CO2, Ferts (both substrate tablets and water-column dosing).
Lighting: On this forum, a lot of people (myself included) recommend AH Supply
fixtures. They sell retrofit kits to fit into your existing hood, or to install as standalone. For your 55 gallon, you might want to look at their 2x55watt kit
CO2: A pressurized setup will break your intended budget, so you'll need to look into diy CO2. A good treatise on the subject can be found here
Ferts: Aside from some form of substrate tabs
, you'll need to look into dosing the water column. That breaks down into two categories: Macros(Nitrogen, Phosphorous, Potassium) and Trace Elements(Iron, Magnesium, etc). While there are a lot of options for these, the most cost effective over time is ordering dry ferts from somewhere like Greg Watson's online store.
To get you started down the road of a successful planted tank, I'd also recommend that you do some background reading about the subject. Rex Grigg's Guide
is an excellent source of info, as well is Chuck's Planted Aquaria Pages
. Once you are comfortable with the info they present, you might then want to look at a more advanced fertilizing discussion
Also, this forum and it's searchable
threads will hold the answers to many of the questions you will have after reading the above information.
Good Luck! and welcome to the hobby of planted-tank keeping.