If you are joining a boxing gym, the only things you really need are gloves, wraps and a mouthguard. The last two shouldn't cost you more than like $10 put together.
Major brands produce everything, from the cheapest (in every sense of the word) gear to world-class professional equipment. You generally get what you pay for.
Mostly cheap, low quality: Everlast, Title, Ringside
Pricey, but high quality: Winning, Reyes
Middle of the pack, few cheap options, some very high quality items: Leone, Rival, maybe Venum and Adidas