Laning Ideally these are the items you want before leaving your lane.
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Get Warp Stone before as first item after everything in Laning
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At this point, you can start roaming. Look to make uneven fights, if you don't kill an enemy 1v1 with your burst. Try to leave, Paradox's sustained damage is terrible.
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Late Improved burst sounds great, but it scales with an enemies max health. Best to leave until last when enemies have higher max health. Use Superior Cooldown imbue on Carbine if good at aiming, otherwise on Swap.
Laning 500s Grab these in order if you're new, you can also pick up Healing Rite just sell later.
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Roaming 1250s Slowing bullets grab in lane if ahead, 26% weapon damage is very good. Barriers for tankiness, enduring speed for movement slow reduction. Spirit items are key for locking a target down. I recommend the first 5 in order here too.
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Team Fight 3000s Mostly Components from previous items. Fortitude > Extra Health. Warp Stone because it's so good earns a spot, however I wouldn't buy it every game.
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Game Ending 6200s Crippling Headshot + Diviner's Kevlar should be the first 2. Silencer if you've built into superior duration early :)