I used this build on my first character. Using 18 dex for other weapons. I leveled it above 150 because I want to take it to NG+.
18 dex gives acces to alot of other weapons. Smelter sword, masterdon halberd, grym greataxe.
Right hand: Great club (fire +5), ascended pyromanchy flame +5
Left hand: Drangleicschield, dark pyromanchy flame,
(optional (poison) parrying dagger, dark infused Transgressor's leather shield, magic infused magic shield)
Head: Hexer's hood. Yes it's overused but fire bns only goes up per 2 points in int and 2 points in faith. So 31 int is as good as 30 int. But 31 int with the hexer's hood gives you 32 int.
Body: Drangleic mail +5 or Masterdon armour +5
Legs: Lion mage robes
Hands: Pennal handcuffs
Rings: Chloranity ring, ring of blades +1, southern ritualband +1, (clear blue tearstone ring or ring of giants +1)
flame weapon, great combustion, forbidden sun, (second) great combustion, (chaos) great fireball, fire whip.
Learn the moveset by heart. It's great but a little on the slow side. Try catching people with follow up swings. Try playing unlocked so you can aim your swings after starting them. Try twohanding. You should have enough agility to dodge incoming attacks. A nice combo is first the twohanded running attack. Immediatly follow up with the twohanded strong attack. Unless the enemy is running a lot of poise this wil smack them on the ground. Stand right on top of them and cast great combustion or flame whip.
As for pyro. The double forbidden sun really wrecks people. Try firing it just as the enemy mist a swing at you. This way they won't be able to roll away. IMMEDIATLY fire the second forbidden sun. The first reaction of people is to immediatly roll after the first hit. You should have enough cast speed to hit the second if you hit the first, just as they recover from their first roll. Most people won't expect the second one coming. Because their vision is blurred, if they know your head gear they know you have 2 casts, but most people fail to realise this fast enough.