To start, we need to first understand his skillset. While they may seem simple, they have interesting quirks about them and I'll provide tips on how you should use them.
PASSIVE - SUPPRESIVE FIRE
Luban No.7's next basic attack after four basics attacks will be enhanced into a strafe, gaining a piercing effect and dealing continuous damage, max of 3 ticks of continuous damage. It deals porcentage damage on Max Health against heroes.
FIRST SKILL - BLOWFISH GRENADE
Luban No.7 tosses a blowfish grenade on the designated area, dealing damage and applying a slow effect. Additionally, grants vision on the enemies who are hit for a short period of time.
SECOND SKILL - SHARK CANNON
Luban No.7 launches a rocket, dealing damage to the enemy hit. This skill has global range and will deal splash damage after impact. If there is a enemy directly in front of Luban No.7, the rocket will knock them back.
ULTIMATE - AIR SUPPORT
Luban No.7 summons a Blowfish Airship to initiate air support. It will drop bombs at random enemies within range at every second. The bombs will deal damage and apply a slow effect. It continuosly grants vision within the airship's attack range
Tips and Combos
To start off, let's talk about his passive:
You'll probably already know this but to maximize the damage, you need to stand still. This is why you need super careful positioning as the enhanced autos are where your damage is at, and you will die easily if you're badly positioned. I'm not gonna tell you to 'duhhh just be in a good position' as that is obvious, but generally, don't attack if the place that you're in could cause you to die
The range on it is a bit misleading. It reaches slightly further than the preview shows. (My apologies for the quality, my phone is not the best.)
What this means is that essentially, in laning phase, you'll end up most likely out-ranging anyone that isn't Garo or Shouyue. And this is very important to know because Luban No.7's laning is very oppresive if the enemy doesnt get help from supports, so you should (if you can) pressure the enemy laner as much as possible with enhanced autos. Of course, there are some lanes in which you can't do this freely, but we'll talk about that in the match-ups section.
Another thing to keep in mind is that it deals damage based on Max Health of heroes. What this means is that his enhanced auto (only the enhanced auto, not all of his kit) will deal damage the more health a enemy has, making him a decent tank-buster. Is he the best tank buster? ehhh no (cough cough Marco Polo, cough cough Di Renjie) but he can work yeah 
Skill 1 - Blowfish Grenade
This skill is the one you'll start at level one, always. If you manage to land it on the enemy ADC along with you enhanced auto, you've already managed to take around 50% of their health, which is HUGE.
Additionally, an enhanced auto followed by S1 and another enhanced auto will most likely full clear a wave, meaning you'll probably reach level two first and apply more pressure.
Also, the slow it has is kinda good. (25% at level one up to 50% at max), mainly because you can safely hit your S2 and your ult will ping them for one tick of damage.
Not much to say, just a decent skill really.
Skill 2 - Shark Cannon
This is hands-down his best skill BY FAR. Mainly due to the versatility it offers.
First of all, DO NOT throw this willy nilly. You'll use this skill for three uses mostly.
- First, and the most obvious one: Getting a kill on someone who is low. It doesn't happen much as hitting is quite difficult, buf if the opportunity arises you should always take it.
- Second: Getting Vision. You can use it in two ways, one as soon as you reach level two to see which buff did the enemy jungler start, or two, to see if they are doing an objective. Keep in mind that the splash damage it does can steal a buff or an objective, but that is super rare.
- And lastly, the one you'll likely use the most, to knock-back people who are close to you. At late-game this is the most important one, if you end up wasting your S2 you're most likely dead.
Now, there are two techs you can do with this skill, both regarding the usage of flash.
The first one is Surprise knockback 3000. You'll use your S2, and immediatelly follow it up with a flash. This will catch a lot of enemies off guard, and can hit multiple enemies. Think of it as a mini Dharma ult.
The second one is the reverse pull 9000. This one is one that you should never use because while it works it is very inconsistent to land. You need to be close enough to an enemy to knock them back, and as you press the S2, you need to time your flash as it lands to succesfully pull the enemy. Don't do this one at rankeds lol, it's kinda bad but it's funny.
Ultimate - Air Support
This skill is a bit interesting, so let's go over what you should do.
Firstly, this is a good tool to use to pressure the lane. You can basically say to the enemy laner 'i win' when you throw it out, and they'll most likely have to retreat.
BUT, and that is a pretty strong but, use this at the appropiate time in early game as this has an absurd 45 seconds of cooldown. (for reference, Marco Polo's ultimate, one that is way more impactful than Luban's, has the same cooldown. game balance is my passion)
This ult is preeeety bad at early, but it scales well into late, especially since it becomes a 15 second ult and will deal more damage due to bigger teamfights.
And also, while it may seem good to send this in in bushes, it isn't the most effective use of the vision it provides. Majority of the time, you'll use this proactively in a intersection you know enemies may come from. Use your first or autos to check bushes, don't waste your ult.
Combos
There are mainly two combos you're gonna do.
The first and most simple one should be the ULT > BA > S1 > BA > S2 > BA. It's simple yeah, but this is not a Yao where there is a variety of combos really.
The second is S2 > Flash > BA > S1 > BA > ULT > BA. This is the flash combo, the reason you follow up with S1 rather than ULT is to have a higher bust of damage.
How to Play
Now that you know all of these, we need to get ready for the action. Keep in mind though, if you are playing rank or peak, Luban No.7 is NOT a hero you'll pick every draft, you should always analyze the enemy line-up and see if you can play him in there. We'll go more in depth in this in the Match-ups section. So with that out of the way, let's get started
How should I play him at Early-Game?
While his early game is relatively weak, his laning phase is quite strong. Let me explain. The damage from his autos are quite low at early, but the range more than makes up for it, especially since his S1 does stupid big damage. At Level 1, DO NOT miss your S1, either throw it at the enemy ADC or at the minions. While a smart ADC will know not to be close to their own minions to not allow you to get too much value from your attacks, if you combo them with your S1 and autos, they will lose the trade.
Some exceptions to this are Hou Yi (He excels at long trades, just out poke him with your superior range) and Di Renjie (You can win against him at level one, but it can be a bit hard. Try to bait him to move closer so that your minions hit him, don't let him get too close though as his S1 does big damage).
As soon as Level 4 hits, you go down on tempo, as Luban's ult kinda sucks ass in early game. Play it safe, no need to overextend and farm as much as possible at this stage.
How should I play him at Mid-Game?
You should have your third item by now, and this is where you'll start to notice your damage. Stick to your team and try your best to not be alone if the enemy is missing, you are extremely vulnerable. Just continue farming and help your team when you can, and at this stage you can also start debating which items you want to have next. We'll go more in depth at the builds section.
How should I play him at Late Game?
Your powerspike is here. In late game, teamfights are crucial, and this is the most important time which you have to stick to your team. At this point, you should be full build, so only push minions to give you time and to push for towers and Nexus, not farm. Your damage will be crucial, so say a lane is being split by an enemy top-laner, your top laner should be the one to go there, not you. Simply put, don't miss teamfights. I've lost countless games simply because i went to defend a lane and my team went in for a stupid teamfight that I wasn't present. It's is frustrating, but it happens.
Of course, since you're an ADC, when a teamfight is occuring make sure you're behind your team, never overextend too much if that could risk getting you killed. (i know I reiterate this a lot but its just such a common issue with people that play ADC)
Also, as a last tidbit, save your S2 here, use it only when someone jumps at you.
Prob should have put this a bit more up, but skill upgrades are S1 > S3 when avaiable > S2.