It depends. Schools have different views and rules on sparring and gear.
For example, we require gloves and footgear, and recommend headgear but it's not mandatory. Hogu (chest protectors) are optional, but rarely used. We don't really care what brand or style they are, so long as they provide adequate protection.
Other schools will require that you buy specific gear.
As far as sparring, without knowing the specific ruleset you're sparring under, the best I can say is:
Hit them more than they hit you.
Can you tell us anything more about your school? What organization is it with? What style of taekwondo is it? Who is the chief instructor?