If you aren't playing at your best, your teammates might say some mean stuff, like calling you "trash", "noob", or other insults. There are always going to be some salty people you play with/against, many of which I have encountered. You can also play in tournaments, which are highly competitive but offer better rewards the better your team does. You can play in Casual, which is not ranked and is generally very chill, or Competitive, where you get a rank after playing 10 placement matches and play others players at your rank.
To get the full experience, you should be online.
You can play offline if you want, but it's not very fun and very limited. The game is free-to-play, but there are some in-game purchases. However, you only have a few of these items by default, and to get more you have to buy them or level up. You can customize your car with hats, different wheels, cool-looking boost trails, and decals for your car. It is easy to pick up and is fun to play with friends. It is literally soccer with cars, trying to hit a ball into a goal, but you're car can do cool things like front or backflips, jumping, and boosting to go faster. This is a really fun game, in my opinion. A loser in GC2 with about 780 hours logged You should put in about 5-10 dollars and get yourself some credits, then start learning the ropes of trading, but be aware to not spend too much, even to get an alluring new item from the shop, which offers overinflated prices for items you can easily trade for. If you should choose to pick up the game and dive into the trading community, be aware of a few things: NEVER trust word of mouth on an item's worth, unless it's wildly rare. There's crazy-looking decals, wheels, and bodies that can be traded for on places like discord.
Basically, Rocket League offers a massive amount of customization options. Finally, and this is the best by far in my opinion, there's a trading scene. There's an active e-sports scene, where players duke it out to secure a spot at the world finals, RLCS, supported by multiple massive gaming organizations. An example is Pulse Fire, who tries to hit incredibly fast aerial shots. Freestylers, players whose only goal is to hit the coolest shots imaginable. However, there are also unique subsets to the community, each focusing on a small aspect of the game. It offers a home for almost anyone, with casual, noncompetitive matches to relax with, competitive matches to level up and brag with, and extra modes such as Rumble, a powerup driven mode with a steep learning curve, Snow day, or hockey, and Hoops, basketball. As the title suggests, Rocket league is a fun title for both split screen and online play.
I got this title during a sale in mid 2019, and have been hooked ever since.