What to do with a 91%IV Arcanine with Bite/Bulldoze

I personally would not power it up. Bite isn't good for defense and bulldoze is pretty bad all around from what I can see. In my opinion that moveset is bad enough that I couldn't even be flexable with it. You don't want to spend dust on a Pokémon that isn't worth it and bulldoze on arcanine is a deal breaker. I'm sorry that he didn't turn out, I've had a lot of disappointments myself lately. I would hang on to him anyways just in case they own day did somehow implement TMs or another way to change moves as that is a high percentage arcanine. I doubt they ever will though. Take care and better luck in the future!

My opinion is to power him up and put him in gyms. He has the 3rd highest max CP and that's all that really matters in the gyms. Being higher means you stay in there longer.

What level are you? Generally you shouldn't be in hurry to spend your stardust before you reach at least close to level 30. It would be really disappointing to find a better one just after you have finished powering up this guy. If you really don't have any other Pokémon to defend gyms, I guess you can go for it if what you want is just high CP. If you have some Vaporeons to defend gyms I probably wouldn't power it up because even despite the high CP, fire type is pretty terrible for defending because everybody have strong Vaporeons to counter them. I don't use Arcanine for defending, but only because I have better options.

Arcanine however is a GREAT attacker and probably the best soft-counter to Lapras so in that sense I would value Growlithe candy somewhat high and wait to find an Arcanine with good offensive moveset to easily get rid of those big grass types and Laprases.

Sadly bulldoze arcanine is pretty useless. Don't use your dust/candy on him. He is one of the only pure attackers and bulldoze ruins him. I love seeing Arcanine in gyms, he is just too easy sadly.

I have two arcanine, both bulldoze. I just left as is and spam quick attack on exeggutors.

I would not power up. I love Arcanine´s gyms when I´m the attacker, and Earthquake is a low damage move. For defending Arcanine I´d prefer Flamethrower.

If water pokemon are at all common in your area (which I'd bet they are in the UK) then he won't intimidate anyone in a gym anyways. He may sit above Lapras/Snorlax thanks to CP, but otherwise isn't very useful. I'd save my stardust for something better.

Transfer and get 2candies before it's too late ;). Sorry for bulldoze