Tracer is a very strong solo queue pick. She isn't reliant on her team at all. Tracer players can impact their games significantly. I'd recommend one-tricking her, as she's effective in all game modes against almost all team comps.
Tracers secondary counters are Sombra, Soldier 76 and Symmettra. Sombra can hack Tracer leaving her helpless. Soldier can land a couple shots then helix rocket her. And Symettras turrets can prevent Tracer from accessing rooms or even kill Tracer if her abilities are on cooldown.
Your main targets as Tracer are the enemy supports. The supports are the lifeline of a team and normally position themselves in the backlines, a position that Tracer's mobility makes her most suitable out of all the heroes to flank to. Mercy is by far the most powerful support and she can res any other support you kill, so if the enemy team has a Mercy she is always the priority target, the other supports come next.
Most significant threat
These are the heroes that will contribute the most in the next team fight. They could have their ultimate ready. They could have an instrumental role, eg. A Rein that's been blocking all your team's damage. Or they could just be really good players. Whatever the reason you target them.
It is perfectly okay to fight a tank just to charge your ult. You may think you are not doing much, but you are actually charging your ult extremely fast and distracting the enemy team.
These are the questions that Tracer players should ask themselves before they ult, obviously these are not set in stone and will not apply to every situation, but in general adhering to these will improve your Tracer play.
1. How many blinks do I have? I want at least 2.
2. Where is my team, compared to me?
3. Will my ult change the fight or push significantly?
4. Where are my counter heroes?
5. If I know my ult can take any single target out, which target has the most impact in this given moment?
6. Do we have a Zarya or another ult I can bomb with?
These 5 conditional statements will greatly help you when you are considering ulting. If you can find a way to maximize these conditions, you will have a better chance at getting the most out of Tracer. If you had to ask me what the most important conditional statement is, my answer would be: Would my ult change the fight or push significantly? If you can check this statement, you still may be able to pull something off.
Tracer’s primary job is to be an annoyance. Her job is to make sure she’s in the back of the enemy team's mind whenever they consider making a push. You should be the reason the Ana doesn’t NANO in time, or the reason Mercy is forced to RES early. In theoretical terms, you should be the computer pushing all the timing and decision making for the enemy team in the game. Taking all of this information in, the most important thing you can do as Tracer is be an annoyance and provide consistent damage. If you cannot do that, you are not doing your job.
Take into consideration that you have your ult. How can you maximize your potential to make sure you get it off correctly? The simple answer is fast and furious. The best thing you can do is go all in with absolutely no hesitation and just do it.
Whether or not you choose to play Tracer on Defense or Offense, these terms apply globally. The common belief is that Tracer is a “Go all in, kill everything and stay in the back line forever.” This is false. The best way to choose a fight is to take into consideration...
What can I do to maximize my team's potential? In most cases, this is annoying supports or going after the carries. If you can distract someone, even for just a second, you have given your team that exact amount of time to either make a decision or make a play.
In terms of actually choosing a fight. The most logical way I can put it is that Tracer is always in the fight. If you can be so much of an annoyance, the enemy team will always take into consideration where you are.
With this in mind, your best chance to actually go in is when the enemy team is distracted elsewhere. This brings in your key element to being an annoyance. When your rein decides to charge in 1v6, or your soldier gets nanod, or your team pushes onto the payload or a point, this is your time to shine.
You will get the maximum amount of damage out because for that point in time, you are not the main threat in the current situation. You will be allowed to have a more free range of movement and fire and can potentially kill the entire team if played correctly.
You can pick Tracer whenever, the map, gamemode and enemy team comp don't really matter. Tracer is the best hero to one trick in the game because of her effeciveness in every situation.
This guide was written by a top 500 Tracer player called Bourne. If you're interested in learning more from him, he has classes regularly on his Discord