You may want to look in the caster forum area. It has a lot of threads dealing with this kind of thing. Here's my recommendations/tips.
There's also good information on pet's, all your spells/etc. here:
http://wiki.project1999.com/Magician#Spells
1. Get the torch as soon as possible. At 46+ try and do as many POH raids until you get your staff of elemental mastery: fire. I'd use that until you get your epic which may be never.
2. Buy a runewood great staff 22/40 2hb - it costs 50-100pp, very commonly for sale in EC.
3. There will be a range of mobs that are dark blue to you. It is much easier if you focus on the lower end of the dark blue. For example, if you are level 40, mobs approximately level 32-39 will be dark blue. Try and stick with the level 32, 33, 34 ones. You will be resisted less, the mobs won't hit as hard, they'll have less hitpoints. Your pet should be able to solo the lower end ones with probably no healing. The higher level ones, you're going to have to either drain all your mana healing or chaining multiple pets.
4. Have bags full of pet summoning gems. If your pet isn't dark blue or higher, reclaim it and recast. A light blue pet isn't going to last nearly as long and you'll end up either healing all your mana away or scrambling to recast another.
5. Remember that a fire pet has to cast damage shield on itself so if your pet dies and you barely get another one summoned before a mob gets on you, your pet won't have time to cast DS on itself. If I know I'm going to have to chain a pet, I stand as far away as possible to give time to cast it and for him to cast DS.
6. You'll have to get a feel for timing. I don't waste mana on nuking a mob down unless I have to. Use that 2hb, you'll hit for 44 at level 20 and save your mana. I got pretty good at my pet getting it down to 1-2% before having it back off and reclaiming it.
7. If I can't send my pet at a mob to pull, I pull with level 1 burst of flame. It costs 7 mana and your pet only has to hit the mob once to get aggro.
8. The fire pets after the level 49 are worthless. They made them into casters and they have like a 1 hitpoint damage shield. Even at 54 I was casting the level 49 fire pet to kill seafuries.