Notes : it could be easier if you are new with Ali to take W out of quick cast, Cast it only when the target is in range in case you want to combo with Q.

Combo one : W ( when in range ) and HOLDDDDDDDDDDDDDDDDDD Q.
Combo two : Flash > Headbutt ( W ) > then Pulverize ( Q ) Used mainly to push a target into the turret.
Combo three : Flash > Pulverize ( Q ) > Then Headbutt ( W )
Combo four : Headbutt into the wall, then Pulverize.

Howeverrrrrrrrrrrr it's not wise to waste your flash, specially if your adc is pushing the lane.

Pros :
1- Insane CC kit
2- Very strong Early and late game ( Specially after level 6 )
3- With his ulti he should simply be tankier than the tankiest tank lol.
4- Can be helpful with almost Every adc.
5- Can be a very good combo with yasuo.
6- You can easily dive under turrets after level 6.
7- You can legally Moooo at your enemies.
Cons :
1- He is a little hard to use.
2- Early game he could be considered to have high cooldowns.
3- His combo at lvl 2 would cost you 130 mana.
4- He needs experience to time your heal in order to deny opponent's farm.

1- Considering that you are the TANKIEST with a very good combo to engage, You should be engaging first.
2- Who to target? Usually the biggest threat to your squishy targets. which are Adcs and Assassins.

Weak Synergy

You would be very limited with what you can do with him, Plus braum always works better with him.

She is quite too weak early game and you won't be able to win trades.

They are good together but I would recommend you to use braum with him.

Strong Synergy

Pulverize > Headbutt close to a wall > Vayne E = GG

Combo the target = Dravennnnnnnnnnnnnnnnnn getting a kill.

Kalista R > You Q > Then W > Then they QQ

Every other ADC not mentioned means they have an average synergy ( would do well if the adc knows his/her skills )