When you come to your first fight practice there is no expectation that you will have any of your own equipment, though good boots, a cup or jill strap, and knee pads are recommended. Ideally, you should let me know a few days ahead of time if you are coming out for the first time and give me a general idea of your sizing so I can make arrangements if needed to borrow a suit that will fit you.
Once you decide that you want to keep doing this, you will want your own kit. What that looks like may change drastically depending on what sort of historical persona you want to portray (if you already have one in mind), but here's a good baseline to get started.
1. Helmet. This is the most important piece of armor and the most finicky in terms of straps and padding. A good basic starter helmet should cost about $150-$300 and have a bar grill for the face. Stainless steel is a good idea in this climate though it does drive up the price. If you don't have a particular time period in mind, a "bascinet" is a good functional style to start with. Thickness should be 14 gauge (mild steel) but 16 gauge is ok for stainless. If you specify "munitions" in your search query that will bring the price down.
2. Gambeson. This is the padded jacket you wear under your body and arm armor. You can get some pretty decent ones from EBay for $100 or less. Doesn't need to be super thick. Not required but makes all the other pieces more comfortable.
3. Legs. You are going to get hit there a lot. I strongly recommend articulated knees because they do a better job distributing force away from the joint. Many people buy articulated knees and then attach their own leather (often with metal or plastic reinforcement) for the thighs. Bokalos armory has some good inexpensive choices http://www.bokalosarmoury.com/elbowsknees.htm Full metal legs are fine too. Covering the upper half of the shin is a good idea. The lower half is unnecessary.
4. Arms. Arms can be tricky because you don't want them to weight you down. All leather is fine if you have enough padding underneath, and a good choice if you're making your own. Articulated metal is good if it's not too heavy - I recommend 18 gauge mild or 20 gauge stainless, or possibly aluminum. Another good choice is an articulated metal elbow with leather forearms and uppers. Again, search for munitions grade to keep the price reasonable. Also, female fighters should make sure to have more than just leather on their forearms due to thinner bones.
5. Neck. The piece that covers your neck is called a "gorget", and any sca-legal gorget should be fine. Leather is ok if it's padded well enough, and leather gorgets are fairly easy t o make. Something with a rigid piece that laps down over the sternum is better than a simple "dog collar" because it will resist being pressed up into your neck. Avoid anything that extends too far out to the side because it will impair your shoulder movement. Having a chainmail or leather drape that hangs off the bottom of your helmet stops most of the neck hits.
6. Hands. The safest and cheapest thing for your hands is a "demi-gauntlet" inside a "basket hilt." The demi covers your wrist, back of hand, and about 1/2 of your thumb. The basket hilt is attached to your sword and covers the rest. There are some very popular molded plastic cup hilts you can buy for under $30 (http://store.fastcommerce.com/icefalcon/hilts-and-misc-items-ff80808117344aab011752db5ac20169-c.html) or lots of metal ones to choose from starting around $45. For your demi I recommend leather or mixed leather and metal.
7. Body and shoulders. These are the easiest pieces to make, and can be done in plastic without looking horrible. You should be able to get all the supplies you need for under $50.