If you’re looking for inexpensive good quality gear, you can find lots on ebay that is slightly used or new. There are tons of one-and-done athletes out there who sell their gear, so for my first few years, I shopped almost exclusively on ebay, especially The Athletes’ Closet. Even today, more than 15 years into tri, I ride bikes I bought new from athletes who bought quality and then moved on from the sport.
Now, if you’re looking for training support, a club is the right way to go to find friends to ride, run and swim with.
The sponsorship thing is more elusive. As several posters have noted, a true sponsorship is going to go to the fast athletes or those with something unusual to offer. I’m a slow-ish runner but I was a sponsored athlete when I was on the Clif Bar Pace Team and traveled around the country pacing marathons and helping large groups of runners reach their goal finish times.
But there are company-focused teams that are more about flying the brand flag and being a nice person who wants to be inclusive. I’m part of Team Zoot, and very happy with the offerings. We get top-quality gear at heavily discounted prices plus very good discounts on partner gear like wheels, sunscreen, helmets, glasses and that sort of thing. In addition, it’s a good support system at races to meet others we may have bet only on social media.