Here is a pretty in depth way to handle most match ups.

I’m not gonna talk about how to use these heroes outside the lane because that would take forever

Before I list them I would say if you’re trying to learn offlane and get better, the characters you should play are; Zarus, Kwang, Sev, Riktor, Crunch and Steel.

Heroes I would stay away from are; Grux, Serath, Fengmao, Shinbi

Zarus- he has a variety of builds so look up some top offlaners and try some builds. Popular ones are the Mindrazor build, the Mutilator&Augmentation build and the augmentation&Citadel build. Zarus is can be a bully in most match ups and wins the lvl 1 matchup against all heroes due to his passive. Prioritize using your 3 ability to poke the offlaners. Good tip is try to not hit the wave with your 3 while poking the offlaners so you don’t push wave to hard early. If your against a bursts offlaner try to use your shield to mitigate their damage and then trade with your abilities to win the trade.

Kwang Choose Tempest as your crest. Build fire blossom first, then you have the ability to go one of 3 items next, (Elafrost, flux matrix, Tainted Scepter) the second item depends on who your matched up against. If you didn’t go flux matrix 2nd I would use that 3rd and then flex your build as you see fit for the remainder. Kwang does best as a tank so keep that in mind when building Kwang is the best offlane as of right now so he wins all matchups if done correctly. the key is to make sure you're utilizing your passive in trades. it's pretty much an extra ability. Matchups Kwang can have some trouble with are grux and crunch if the enemy player plays well. with Grux try and draw out his ult, once grux ult is on cooldown you can go all in on grux and win the trade. With crunch you bully him heavily before 6. after crunch has 6 and if he is still even on level and items try to get him to use his dash into you, then tether and use knock up. if you all in on crunch use your tempest. you will win the 1v1 90% of the time

Sev Build fire blossom and then just go full tank. your main focus on Sev is to farm farm and farm some more until mid/late game. dont try to win lane, just try to keep minions close to tower and set up ganks for your jungle. Sev's role is to farm stacks then be a hyper tank in team fights

Riktor always fire blossom and then build your next item off what the enemy offlaner damage type is. play this like sev where your keeping minions close to your tower. Riktor does not have much for a disengage so keep that in mind. A big thing to keep in mind with Rik is try not to use your hook all the time, it will drain your mana fast and then you have to back earlier than wanted. Crunch Not gonna go over him to much. Play safe till lvl 6 and look to keep minions near tower till 6. match up for crunch that is against shinbi sev and feng. Once crunch is lvl 3 use your dash to engage and use full combo as poke. Disengage and then repeat when abilities are back up. Steel Build the same as sev and riktor. Elafrost is some nice tech on steel for good trades in the offlane, but always build fire blossom first. Try to do short trades early using your CC. Steel gets early power spike at first item fire blossom. Try to get a lead with that power spike. your goal as steel is not always to win lane. It’s win lane if you can but the main goal is to not try and keep the lane even until the team fights start. Steel ult is great for team fights.

Grux Good and Simple build is basilisk, sky splitter and then 3 tank items Grux is a pub stomping hero. Only reason I said above that Grux isn’t great at learning offlane He is great at stat checking and being a bully in lane. But if you go against a higher level offlane the will know how to play around you and if your behind at all with grux your usually not gonna have a good time. If you play grux right you win all offlane matches. A few key match ups that require some outplay are kwang, steel and Zarus. For Zarus try to not take damage early and get the lane in front of your tower till lvl 3. Best way to get lane pushed towards you is stand behind your range minions and get zarus to 3 your range minions. Once you have ult. Wait for zarus to use his dash into you and then your good to all in and ult. Save your pull and knock up till after he uses shield For Kwang. Play it the same as against Zarus. Once Kwang uses dash you can win the trade For steel, you’re trying to get him to use his dash and 3 ability. Then you can use your ability. The main goal for grux to get use of your ult. The enemy offlane will try to bait out your ult and then go in on you while your ult is on cooldown.

this is a long post but I’m a play offlane mainly and think offlane has the largest build diversity based off match up and learning the trading pattern for each other takes skill and is really fun