There is no way a necro can survive whit only a fire golem even tho they are very strong and you cannot base your necro on the fire golem itself. If you want to use a fire golem i would suggest making a summoning necro. Fire golem(max), revive(max), golem mastery(~5~), summon resist(~5~), bone spirit(max) for unique monster, lower resist(~15~ whit items)
and rest in skeleton mastery to make revive stronger ;-). You will need huge ammount of mana level 20 fire golem cost 240 mana and revive 45 so if u have level 20 revive you will want to cast it 20 time 20*45+240 = 1140 and thats if u have maxed both whitout item bonus. You will mostly cast fire golem in town and get healed but there still 900 mana needed for revive so i really suggest you have at least 700 mana whit item and lot of mana regen you will need it a necro like that will always have a good ammount of revive arround him so you wont need much str for armor (aim for +skill and mana regen items) then focus on energy and then some vit. Dont use all your stats/skill point when u not sure what you still need to raise just play whitout them and look what need improovment !

Advantage : Safe, easy, fun
Disadvantage : Huge need of mana, not killing very fast