Read the rule book.
Don't blame yourself when the rifle is the problem. If you're not shooting master scores within a few matches, it's probably the rifle. Often, it's not the indian, it's the arrow.
Don't skimp on the rifle. Do skimp on every other piece of gear until you know why you want it. "Because it's cool" is a valid reason, just know that's what you're doing. You don't need 90% of the stuff discussed online to be hyper-competitive. The difference between budget gear and stupid expensive gear is usually convenience or just general quality, not function.
Aside from the rifle, one piece of gear you do want to splurge on is a shotmarker e target. They're a bit spendy, but the utility/dollar is high. They're great for practice, and if you have a good chronograph (a labradar, for example), it can help a lot with things like ladder tests. Autotricklers are also really convenient, but not strictly necessary.
Learn to do load development PROPERLY. This is a big topic, but it's one that holds shooters back. There is a lot of bad advice online, this forum included. It is what it is. Take the time to figure it out and understand the whys.
When setting up your rifle, just copy what other serious shooters are using. Don't reinvent the wheel. For .308 that means a 185 to 200 grain bullet, a freebore of about .170, 10-11" twist, small primer brass (this is important !!!!), 30" barrel, a 40ish power scope, and a stock that looks somewhat like a McMillan XIT. Ski type bipods are the most common. This is not to say you can't shoot well with some off the wall stuff, but there's a reason most good TR rifles look pretty much the same.
A caveat on bullets. It's not bad to start with those 175s and then work your way up to 185, then 200. The lighter recoil is nice, but more importantly, your wind misses will be more obvious and that helps with learning.
And finally, be wary of sponsored shooters. If someone is constantly promoting a certain brand out of the blue, chances are they're getting some sort of compensation. There's a lot of good gear out there. Don't fall for the marketing traps.