it's a thing we all know: your lane is going fine, got a kill, and assist, and you're 20 cs ahead. Then midgame comes around, and you notice that Riven and Orianna have more than 15 kills together at 13 minutes, because karthus and shen have been attempting to see how many seconds of grey screen they can pack into a single game. Any tips on how to take it from there? you may be doing fine, but comparedly you're 3k gold behind each of them, so what to do?
You feed yourself so they dont feel left out
When both other lanes feed it's very tough, but there are a few things that you can do to increase your chances of winning.
Lastly, don't ever rage at them at this will hurt your chances the most. Everyone has bad games. Hope these tips helped somewhat.
I had recent games where this actually happened, one with Kennen and one with Viktor, both in the top lane.
In the game as Kennen, I won my lane really hard against the enemy Udyr, but the other lanes were losing hard. What I ended up doing was roaming to the mid lane to help out my team pick up kills and such. I basically single-handedly turned the game around by roaming, helping out my team, and using Kennen's teamfight power to decimate teamfights. I remember one midgame teamfight where I ended up setting my team up for an ace, and I was the only one to die in the process, despite being down at least 5-7 kills.
In my game on Viktor, the difference was less dramatic: I had a CS lead, but did not get any kills despite the lead, and I eventually died to a four man gank top. How I was able to win the game (in actuality, force the enemy team to surrender) was, again, I started roaming to help my team pick up kills all over the map, and eventually my team had gone from a kill deficit to a large kill advantage in the span of 5-10 minutes.
The key thing to take out of this is that you need to help your team as soon as possible. Roaming to secure objectives or kills is probably the most important thing you can do with a lane advantage. Notice that in both of the games I mentioned, I was playing in the top lane, which is the lane that can help out the other lanes the least, yet I was still able to take my lane advantage and push it through the rest of the game, and help secure my team a win despite top being the one lane least likely to impact the rest of the map.
What kind of champion are you playing?
For example, auto attack champions, when fed, tend to be phenomenal tower pushers if left unchecked. Good warding in tandem with shoving towers can quickly gain tons of map control for you team.
where are some good ways to help. champs like warwick 
auto attack champ will eat through towers with his W same with other champs in his lane if matched with another CC like lux. lane comps are important. if the other lanes have a bad comp your best bet is to try ganking or setting up a gank under a tower with your CC ability team mates.
lets say 
is doing good in her lane you can ask for her to assist and set up the gank this takes a moment to type out but if she is paying attention and has map awareness she will already be on her way to do just that. if top lane is died 3 times its a sign they need help with an early gank or two.
champs with no escape mechanic like 
before they get there ult may die easy against a champ with good CC in which case she will need some help to get back on her feet this might mean you need to do a little carrying or paying attention to team health bars and jumping lane to help, good warding can also help with map awareness
pinging a warning sign near there position can also help make them aware they need to back off and heal.
also getting a voice chat to use with teams can improve communication skills as well. i suggest Raidcall or teamspeak. Raid call just needs a room number and takes little to set up.
Take turrets in other lanes really helps take down the pressure on mid also good junglers
Key if Karthus is mid vs an assassin KNOW that he will need help and help him push the lane and take the turret.
Make it a disadvantage for their mid champ to roam and leave mid undefended.
You roam with the jungler into another lane and try to take the enemy out or take a tower.
