Try every hero and be able to fill roles if needed (e.g. team needs a healer? Make sure you're able to play one). And don't go into competitive too soon. Make sure you feel comfortable with the game and its overall playstyle in order to be able to compete. And try not to be toxic or salty other than that enjoy
biggest tip is that whoever you main first 9/10 won't be your actual main. it's crazy when you start diving into the game you start to learn other heros and bam one just clicks and you'll switch. so practice. have fun. do a shit ton of quick play. and most of all be a team player.
that too. be versatile. sometimes it's smart to switch heros after using your ult so you can do a different strategy with your team. like on junker Town. once you get inside the building switch up your team comp. it completely disrupts the enemy tea.
Play the game the way you want to, don't let the toxicity of others latch on to you and make you toxic or hurtful to other players and just have funnnnn .. it's a game after all
Definitely be open to play different characters that you don’t think are your style. Dva and tracer are two of my mains and I had absolutely no interest in playing them when I first started, so your interests can change with time.