Hi Alejandro, as Russ said, you will need a lot of equipment to get started playing hockey. In addition to what he said, you'll also need a hockey stick and a bag to carry all your gear. Play it Again is an excellent place to go for most gear, although a common belief in in the hockey community is that you should ideally purchase a new helmet rather than a used one. This is because helmets are certified by an organization called HECC (you should see a sticker with this name on helmets, if not, then it's not a safe helmet), and they are certified to be good for 5 years, or until there is damage done to the helmet. So, if you buy used, you want to be careful because you may unknowingly purchase a helmet that is no longer safe for you to wear. Head injuries are no laughing matter, so you'll want to best protect yourself. Play it Again does have some new equipment, so that would be a good start. You may also want to consider your local rink pro shops, as they are often running very competitive sales in order to take some business away from online retailers. You will also need hockey tape, which is only few dollars per roll, and will last awhile.
However, if you want to be a goalie, you will want to consult someone who knows the required goalie gear, as it different than that of a skater. Goalies have totally different gear, from head to toe. So, if that is your desired position, be sure to get position-specific gear so that your can best protect yourself while playing. Hope this helps, good luck!