In the beginning of the match what you want to do is switch to Cannon mode and kill as many minions as possible while trying to stay out of fights unless a team member is with you but keep your distance if you going solo.

In the middle of the match you can do some damage but you wont win if there's more then one enemy champion, so try to coordinate with your team members or try to gank enemy's when their not suspecting it.

Near the end of the game if you have everything in this guide you should be able to gank the enemy's, and fend off anyone that try's to stop your your team from destroying the turrets and anything else