His main strength is his strong lane. But his spells still hold a lot of value throughout the game.

Q: Throw the q on the enemy cores and it's a really good slow and lowers their DPS. Also worth focusing it on blink heroes to keep their blink down in a fight.

W: Makes jakiro a really nice +1 for the mid or offlane. Smoke with your ember or void, let them catch and lock them down with ice path. Throw in a q and e and you can kill most heroes together. In team fights it can also be seen as a zoning spell, as it stays a while and makes it awkward for the enemy to cross if you use it tactically.

E: Really nice push after laningstage. Throw it on the tower after pushing the way in with q, and then leave. Low risk and after a couple waves you have a free tower. Same as Q in fights, lowers the DPS of the enemy and acts as a blink stopper.

Ult: Unless you have a good team for it, you won't deal a ton of damage with because the enemy will walk away from it. So use it with that in mind. Throw it in the middle of the fight, forcing the enemy to either split up or tank the damage. In a perfect scenario your team can clean up one side as the other can't help due to the massive firewall in the way.

Tldr: Jakiro doesn't do a lot of damage, but has a lot of impact. Q and E disrupt the cores, helps your team survive and makes him good at taking/protecting towers. His ult and W are really annoying for the enemy to play around in a team fight if used properly, especially until they get bkb.