Hey everybody! I'm back again after a long break, and today I'll bring you an adc that's actually not off-meta (shocker, I know). If you're interested in my off-meta stuff I'll post another guide later today. Now, back to the guide:
I've been playing Samira since she was released in PBE, and I joined the Samira mains Discord server as soon as it was created, and started modding it after a few months, so I've seen every type of build while it was being created and followed every new thing about her very closely, if you are interested in more in depth information, you can join us here and ask all you want:

https://discord.gg/gDrr35PA4k

Samira may be really good right now, but you can't just blind pick her. She's easily counterpicked by heavy CC tanky champions, and you can get screwed over by your support picking an enchanter. Try to avoid Samira if your support picked an enchanter or mage, and if the enemy team have easy ways to stop your early snowball.

I don't usually add combos on my guides, but for Samira, they are the coolest part about her kit, so here you have some of them:

Most useful combo: Used when your engage support combos somebody

AA | E+Q | AA | W | AA | Q | R

Most used combo: This is gonna be your go-to in every teamfight

AA | Q | AA | Q | AA | E | R

Practical Combos: These are used in lane/1v1s.

AA | Q | AA | E | AA | W | R

AA | E+Q | AA | W | AA | R

Fast (but impractical/inconsistent) Combos: Mostly used to show off.

AA | Q | W | E | W2 | AA or Q | R

AA | W | E+Q | AA | W2 | R

AA | W | E | Q | AA | W2 | R

Samira is a lane bully (as long as you followed the steps you need to follow in champ select), so abuse that. Try to deny cs pressuring them off the wave with your support and get an advantage that way, abuse every mistake they make by going in and winning a trade. Use W in a smart way to block important abilities and win the trades or get yourself out of sticky situations. Remember to deep ward to avoid ganks since you're mostly gonna try to play agressive.

In case you're starting to get behind...

Stop fighting for no reason, they have an advantage and you will most likely die or take a bad trade and be forced to back. Play it smart, freeze under turret and wait for a gank to get yourself back into the game.

Did you snowball and now you're trying to win the game off that, or did you fall behind because of whatever reason? Your playstyle in mid-game remains mostly unchanged regardless of the situation: Auto Q the frontline repeatedly to get stacks if it's safe, wait for them to use their important CC, then E in, and R. A couple of good teamfights and you should be winning the game!

So things went bad and you couldn't turn your snowball into a win? Well, this is a tricky situation. By now, you probably got outscaled by mostly any adc. At this point, trading your life for a value target might be worth it, otherwise, keep playing the teamfights the same way. Splitpushing won't do you any good.