Hextech Gunblade is hardly viable on Katarina, or anyone anymore, this ain't season 2.

Take one of those mastery points out of Hardiness and put it into Veteran's Scars . 30 HP > 1 Armor.

Flat Magic resist glyphs are more useful in the solo lane to reduce incoming magic damage. You even say in your runes chapter flat is the way to go, but your cheatsheet says otherwise. Make them the same.

Nothing is maxed out by level 9, pick a skill and max it first. Don't spread points out between them.

^

Gunblade, Liandry's without Rylai's, wrong skill sequence, wrong glyphs, no C2V, etc.

It's short and decent. I like it in a way, but there is no intensity to it :/ Your build is nice.. But I highly prefer not buying liandry's torment mainly because there is alot better items to buy than that .. maybe you can check out my guide?

Down below

Your guide is fine and I am certain you seem like a good player, I know a good Katarina when I see one ;) thumbs up

Walls of text...

No-one will have ~2k gold on their first back, and even then I personally think haunting guise would be better...

I think scaling health seals are better.

One sentence explanations, very short and not in-depth at all. -1.