Tremere are all about Thaumaturgy IMO. That's what makes them unique, so I'd go for that in the long run.

Blood Theft is super good, because it's a net blood gain if you don't move before the return, and even against supernatural enemies it usually stuns them.

Blood Shield is great for a Tremere because you set it once and it lasts forever until it breaks. Just don't forget to turn it off before you go out in public.

Against supernaturals, Blood Strike works great in combination with Blood Theft.

Blood Boil might be the most fun discipline in the game for mass murder. As long as you're hidden when you cast it you can get away without a Masquerade Violation. It doesn't work as well against supernaturals though.

Carry a backup weapon just in case.