Firstly, in lane you need to remember that at the beginning of the game you aren't even remotely tanky, so play like a burst mage until level 3, where karma gets her CC and her shield/speed boost.

after you have bami's you're actually strong, so you can actually affored to play in their face a bit as long as they don't counter you.

harrass the enemy with grasp procs and Q, this makes winning an all in much easier.

if you get tower dove, the first thing you do is Ult+W them, then shield yoourself and Q them. this almost always ends in a free kill, even a double sometimes if the jungler joins your laner.

Roaming is something you do sparingly. for example, don't roam:
- when your laner backs to gank a lane
- to 1v1 anyone
DO roam when:
- your team needs help securing herald/drag
- there is a fight top river/top jungle
- mid is getting destroyed and you need to hold tower for a bit

basically, no roaming unless absolutely necessary. these are rules I try to follow and I have seen good success with them

I want to make it clear that you will almost never carry a game. you can, however, make it nearly impossible for the enemy carry to function properly. you are a fantastic teamfighter, throwing shields and movespeed increases at your allies and throwing cc, slows, and surprisingly high damage at your enemies.

you are also very good at shutting down the enemy top laner, even if you are doing poorly. you can theoretically win lane against every champion in the game, aside from fiora, who you ban every time.

Let's start with core items

Frostfire: there are two main attractions to frostfire. firstly, the 100 health on it's mythic passive is 400 extra health late game, and since karma's heal is based on missing health, a larger health pool means more potential healing. second is the slow field on basic attacks every six seconds. this deals %max health damage and the slow is great for karma, who can already kite quite well.

Ionian: putting out as many abilities as possible can be important in a lot of fights, and as such ability haste is an important stat to have.

Spirit Visage: the heal boost on Spirit visage makes Karma haeal for a ludacris amount. you can easily shrug off two high damage champions for far longer than one should be able to with this item.

Situational items

Demonic embrace: a very good item, giving AP based on your max health, however sometimes karma needs more tank stats or resistances rather than damage, and so this item is only good against low damage/high health enemies.

Thornmail: the classic anti-heal item for tanks. there are better items to build for armor though, so only consider for the antiheal.

Winters approach/Fimbulwinter: sometimes you need to go from fight to fight very quickly, and don't get a chance to back and get mana. with the shield passive that goes off whenever you root someone, it provides great durability in a fight, and keeps you from running out of mana.

Warmogs armor: giving a massive amount of health and health regen between fights, it can allow you to participate in a large fight, and then immediately be full health somewhere else on the map.

Frozen heart: if armor is a particular concern, you can build this instead of fimbulwinter, as it grants you armor, mana, and some of that sweet sweet ability haste karma loves so much.

Titanic Hydra: this item is not recommended in most situations. however, it can be very powerful in the right situation. if the enemy team has built a lot of MR and you need some damage to stay relevant, titanic hydra fills that role nicely. tank karma already auto attacks quite a bit, so making them do more damage can be a good gameplan.

Dead mans plate: Karma has great movespeed with her E, and can even slow and root her enemies. sometimes, however, she needs more speed. While also providing armor against AD, it is a pretty solid item to build.

Anathemas Chains: as good as this item is against a singular champion, you'll almost never want to build it. most of the time there are multiple people on the enemy team to be wary of, so general itemization is usually more effective. against a single carry however, especally a tankbuster like vayne, it is one of the best items in the game for karma.

Hullbreaker: being honest, this item isn't as good as it usd to be. the extra stats can still be good if you are being left alone by your team to 1v1 or 2v1, but since the nerfs for ranged champs there are not a lot of situations where you need it, plus Karma is a weak pusher so splitpushing is not a viable gameplan for her.
keep in mind, there are still situations where it's good. against someone like shen, who roams constantly, hullbreaker can discourage roams by getting more pressure on his tower. if he does roam, you get free plating as long as your wave management is good, and if he dcides to stay in lane, you take away his one strength. good item against these kinds of matchups.

Force of nature: standard anti magic damage item, not much more to say.

Gargoyle stoneplate: more of a teamfight item. better choices in some cases, but against a high damage team with an even spread of AD and AP, there is no better item.

Abyssal mask: when building demonic does not yield enough damage, build Abyssal mask. this not only grants a lot of health and MR, it massively increases your damage.

cosmic drive: if you need more tank stats, then stay away from this item at all costs. it does, however give: move speed, AP, Ability haste, and even a bit of health, along with an in-combat bonus to AP and movespeed. great all-around item for tank karma.

Rylai's crystal scepter: when going for AP, you can't go wrong with Rylai's. it even has a slow, which makes kiting so much easier. great item when damage is a consideration.

Randuin's omen: powerful teamfighting item, especially when the enemy team has a lot of auto-attackers.

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This section will be updated with new/changed items, but is done for now.
Last updated: 3/24/22

while it is true that every champion must be treated a bit differently, some champions are seen often in toplane and all of them must be handled very differently. I will share how I like to deal with them, and maybe it could be helpful to someone reading this.

Irelia: you need to consider exactly where you two are and how far she can dash. if she get's on top of you, tryign to win the trade by staying and fighting is a fool's errand. when she dashes on me, I shield her initial damage and ult+W her. my hope is that my shield will give me enough movespeed to both get away from her and easily dodge her stun. after the Ult+W, throw a Q to slow her and deal some damage. she will hopefully not be able to reach you before your root keeps her in place, and if that happens you're out!

rengar: not a common pick, but an annoying one. the bush side of the lane is OFF LIMITS until you have Bami's and T1 boots at least. keep riverbush warded and poke like you've never poked before, once you have mythic he won't be able to deal enough damage to you to win a fight, (unless you or someone else on your team has fed him some kills of course).

shen: his main play will be tou dash at you and taunt you. try to shield before you are taunted, and after the taunt immediately ult+W him. throw a Q and auto him as much as possible while keeping a safe distance. if you fail to shield before being taunted, once the taunt wears off use your ult+W, then Q, then shield yourself. in the first instance you win the trade, and in the second it's relatively even.

yorick: play at a distance and poke. if his ghouls get thrown at you shield and auto them. if stuck in his cage the first thing you do is immediately Q him, followed by an Ult+W. if he gets within melee range, shield yourself. this whole time, be attacking his cage to break it and get out. you can then keep harrassing at a distance. I've seen yorick's die because they walked up to me, and then coudn't get to me or get away through all the roots and slows.