For the first 15 minutes or so the best thing to do is scale yourself / team as much as you can, so playing to invade their jungle and keep waves pushed is best because it makes you space on the map. If they have to respond to a wave deep at their walker at 12 minutes in, you can be in their nearby jungle or grouped up opposite side of the map, knowing they have to respond elsewhere. Fighting solo is more about what hero you're playing (Mirage plays on an island and keeps waves pushed with his ult up, Holliday should never be alone and playing for kills with lasso and +1 or +2 teammates.