Yeah, the traditional split-pushing and roaming style.
Snowballing
You need to get fed early. Poke your enemy down and then all-in with leap, heartseeker, and Ignite. Use the gold to buy an extra sword and poke your enemy down more once he comes back to lane. Try for another kill.
Once you’re 2-0, your opponent will have a very hard time dealing with your poke. You now have options. Deep ward and start pushing the wave while zoning your opponent with your poke. If your jungler can take an early dragon, then ask them to head bottom and take it as soon as the enemy jungler appears on your wards. Do not try to 2v1 unless your opponent is very low and you are healthy.
Alternatively, if your jungler can’t do an early dragon, then ask for them to come topside and dive the turret once you crash your giant wave into it. Let the minions tank the turret aggro while you walk under with your jungler. Kill or drive off the enemy laner and then take the turret. You are now free to splitpush and roam.
To splitpush, ward deep and shove the wave. If the enemy jungler appears on your wards, then run away. You can then either roam or ult to the midlane if the enemy midlaner is overextended, invade the enemy jungle through the bottom entrance if the enemy midlaner can’t help, or run across the map and ult the bottom lane if it’s overextended. If you can’t do anything, then recall, buy items, and try again.
Objectives
You need to help your jungler secure the Rift Herald and Dragons. The Herald will help you take the middle turret, while Dragons will give your whole team buffs. Forcing the enemy jungler to come to the opposite side of the map will let your jungler take these objectives freely.
You also need to start tower diving enemies who attempt to waveclear under turret. Take their turrets afterward. You and your team need the gold from kills and turrets to start winning skirmishes. To end the game, you have to head botside, ward deep, and force the enemy team to devote more than one player to stop you. If they send the jungler, then tell your team to do Baron. If they don’t, then tell your team to siege the midlane turret and possibly send another splitpusher topside.
Once you have Baron, get your sidelanes pushing and group with your team. Do not frontline. Wait for the teamfight to start, the big crowd control spells to be used, and then ult into the backline. If you’re fed enough, then you should have Guardian Angel, letting you kill both enemy carries. With the enemy team aced, tell your team to take the enemy inhibitor while you take an inner sidelane turret.
Tell your team to leave the base, recall, and group bottom while you head top. The game is practically over now. You can kill anyone 1v1, and your team can win 4v3 with Baron. If you think they can’t, then get the top wave pushing and group bottom with them to repeat the process. Then repeat the process top. With all three enemy inhibs down, your team can walk into the enemy base and end the game.