As sylas, Level six is a variable power spike depending heavily on the enemy team's composition. He will have to ensure that he takes the proper ultimates to be effective in the game. 

Level 3 is a decent power spike as it allows him access to all his basic abilities. He will also dish out a lot of damage during duels and heal himself with his W when needed.

The first item component will bolster his overall damage and will let him take over fights with ease. It will also help him with his Jungle camps and his overall survivability in the game.         As sylas, Level 6 is a variable power peak highly dependent on the composition of the enemy team. It will have to make sure that it takes the ultimate appropriate ones to be effective in the game. Level 3 is a decent power peak as it allows it to access all its basic capabilities. It will also dry up a lot of damage during the duels and heal with its W when necessary.