One Hook, One Kill (Bomb/Beam)

HPW -> MR -> SS -> IN -> MR -> ES -> SB -> DB

SSB -> EB -> ES -> MV

IS -> SC (ULT) -> WS -> IR (Bomb) -> IB

Very early laning can be tricky due to your gun's very short range at low levels
If you're in a duo lane with good follow-up grab Hook first, otherwise get Bomb first
If you're confident about your lane opponent, go for early Bomb stacks by playing forward and using veils
If not, play defensively, focus on last hitting and securing/denying
If your opponent(s) push towards your guardian, Hook them into guardian to secure an easy first kill
If they go for melee secures, Hook them while they're stuck in the animation
If they don't go for melee secures, you should easily out-farm them with denies
Once all abilities are unlocked, use 180 Hook -> Uppercut -> Bomb into guardian if they're on your side of lane
If they're pushed, use Bomb -> Uppercut on a low health (flashing bar) enemy minion to damage them under their guardian (minion dies on landing, resulting in instant bomb detonation)
When tier 3 camps spawn, use Infuser -> Bomb -> Ult to kill them easily for extra souls.

Roam to nearby lanes to assist your allies
Bebop has great ganks due to his Hook
If the enemy doesn't see you coming, run up behind them and Bomb -> Uppercut them towards your teammates
When they try to run, reel them back in with a Hook to secure the kill
Don't forget to grab jungle camps when between lanes, Bomb gives you great clear for both camps and waves (you can literally Bomb and keep running to get T1 camps and double Bomb T2 camps)
In teamfights, you should focus on picking off an enemy squishy with Hook
Either Uppercut them towards your team or directly up if your team is already close to you
Just don't Hook a Dynamo, and if you do, cancel Hook before he gets close
If the enemy commits to an engage, get some height and ULT
You can also ULT to secure kills on fleeing enemies or directly after your combo for big burst damage
Optionally, you can get Majetic Leap to get height and good angles for ULT
You can also use self-Bomb with Warp Stone or Phantom Strike to jump an clustered enemies for massive AOE damage (just make sure your team is following you in)
Lastly, you have fairly high mobility with this build, use it for Urn, ganks, and split pushing.

Late-game Spirit-Bop is more of a play-maker than an assassin (though you can absolutely still delete single-targets)
Double Bombs on either yourself or an initiating teammate can burst whole clusters of enemy players
Hyper Beam doesn't result in guarunteed kills (usually), but it synergizes with CC ULTs very well, and it always forces a response from enemies: they either get behind cover, rush you with hard CC, or die
You basically have a mini Seven ULT with half the cooldown
Just make sure to use Warp Stone or good positioning to get enough height that you can hit the enemy team and avoid most CC
Now, let's talk item counters for Bombs
There are 2 items of note: Debuff Remover and Etheral Shift
If they went Debuff Remover, laugh and use self-Bombs instead of target Bombs
This will completely invalidate the item as a counter to you (though they might still get it if you have a Pocket on your team)
If you're really spicy, you can even double self-Bomb before you Hook so that they die immediately upon reaching you
Etheral Shift is more problematic
Even if you self-Bomb, they can still time the invlunerability to stop the damage (and stacks)
Your best bet is to either bait it out with a single Bomb, then double Bomb when it's down, or to double self-Bomb then Warp Stone into a team fight to hit their whole team while they're distracted
Curse is also a great option, and you should be getting it by this stage anyways.