For a VtM session I'm taking part in – we're playing using the Vampire 20th Anniversary book – I have created an interesting young Giovanni necromancer. “Young” is a keyword here – my “powers” aren't really that strong (yet). The character has the mind of a scientist (working in a morgue in New York as his “day” job) and certainly knows his way around social situations.
The way we handle social aspects is through role-playing, where character stats only serve as a description of said character and using dice is rare. Actual combat is handled through dice rolls almost exclusively.
Now, the majority of our time during sessions is spent lying, plotting and generally role-playing, and we've only had one big combat encounter thus far. However, I found that my character was next to useless during that encounter. I did get a few lucky rolls and managed to do some damage, but that was really just luck.
Thus far I have the “standard” starting Sepulchre Path at level 3. I feel my characters combat prowess could be vastly improved with the selection of a proper necromancy discipline. I'm not looking to have my character become death incarnate in combat, just be able to actually help in a more reliable manner.
My character has a cane which contains a hidden blade (because of course it does), but that's a last-line of defense. He has proven himself to be pretty good with various chemicals, especially narcotics (don't ask!). At one point he has created a potent mixture which did work on a vampire (albeit a particularly susceptible one).
A thought did cross my mind to have the hidden blade coated with some form of chemical, but that still means he would need to attack with said blade. In the simplest form it could be something that burns easily and long for a fiery-blade effect, but THAT in turn means my character is just as likely to be afraid of it as are his enemies.
Finally, the character has a ghostly companion. However, the relationship is more “friends” than “master-slave”, and he won't force the ghost to do anything the ghost doesn't feel like doing. Essentially this ghost is controlled by the DM as a “give out tips and freebies” kind of option while my character can make simple requests.
So… which necromancy discipline path could be most useful for combat?
I could pick The Bone Path – given that my character works in a morgue and has access to corpses. However, that'd be only useful if he were to fight in the morgue. A corpse might not be readily available everywhere. I would like to keep the theme of the character intact. The character is well connected and he could just as well learn a discipline belonging to another clan it… just… wouldn't fit, I think. He embraces the core Giovanni concepts and enjoys his work – why would he be studying a discipline not connected with necromancy?
Regarding minions
My character does posses a ghoul, a helping hand working with him at the morgue. The ghoul is far more "brawly", so he could, in theory at least, be of some use in combat. That said, given the supernatural nature of combat I'd fear for his life – he is human after all. That, and my character would need to take him wherever he went. This is troublesome and deprives my character of a valuable “behind the scenes” resource.
Creating more ghouls requires an official permission from a vampire higher in the chain of command, so creating disposable bodyguards doesn't seem like an option.
Finally, even with bodyguards of some kind that still leaves my character to sit idly on the time-out bench while others are having all the fun. It would be really nice to be able to do SOMETHING. If not direct damage, then some control. Otherwise he'd have to maniacally laugh while his minions are killing / getting killed, which doesn't fit the character one bit.
Best Answer
Trying to answer the actual question
I have looked at the V20 necromancy paths. I suppose there are other paths on the splatbooks, but I don't have the time to make a research.
Generally speaking, necromancy paths seems not oriented to combat. I suppose that's for a reason. A Giovanni necromancer is supposed to be subtler than that and not effective on direct action. With the help of the ghosts, he can be always ahead of his opponents, and prevent the confrontation, or address it always in advantage. I would try to use those resources. Prepared vampire is worth two, or however that idiom translates into English. More action-oriented Giovannis go for Potence.
But you were asking about Necromancy paths effective when you are already in the combat situation. I think you pointed out the better choice: the Bone Path. How to use it outside the morgue? Well, as I said before, the anticipation is your advantage, so if you know you are going to enter combat, you can bring the corpses from the morgue (assuming you have enough dots). Also, in combat, people tend to die, so sooner or later you could have a corpse to take control of. Sure, it's not as direct and deadly as launching flames at your enemies, but let face the fact you will never have anything like that.
It's a shame that Giovanni killed all Cappadocian and Lamias because their paths seems far more useful in combats. If you and your Storyteller wish and can build a convincing story in which your character can learn the lost paths of "The Corpse in the Monster", "The Grave Decay", or "The Four Humours" you would get what you are looking for, or at least the closer you can get with Necromancy. But as a Storyteller I would make it very hard and you would end owing a lot of favours. Be warned!
But you should consider...
I play non-combat characters very often. There's something that have proven essential when your security is threatened: Retainers.
Have a bodyguard or two. They can be more suited to combat than your character, and your character can buy time to do some tricks with them. Ideally they would be ghouls, which supernatural powers would make them deadlier in combat. But if you cannot create ghouls, you can hire regular goons. A Giovanni vampire usually has the resources or contacts to do this; if not, the family can sure help. Dominate 3 would be very useful to avoid breaking the Masquerade, but other means can be used.
This way, you can still focus in doing what your character knows well, necromancy, social work, finances, or whatever.