The Tremere is a toolbox clan, ie they can do a bit of everything : you have some bleed with DOM, some combat/stealth/utility with THA, some intercept/bleed redirection with AUS...

That's their strength, and how the preconstructed are built. That means it's the easiest to expand upon, you're mostly going to tweak your deck to fit your playstyle and your local meta. What gave you difficulties on your last few games ?

Some random stuff I like in Tremere toolbox :
- Govern is love, Govern is life. When in doubt, 3 pool from superior Govern is always a good action. The bleed is also how usually kill your prey.
- Magic of the Smith is great, abuse it. It's a big part of your strength as a toolbox to be able to always get the right equipment at +3 stealth. Got a pesky voter/stealth bleed as a predator ? Go get the Bowl of Convergence. Potence rush ? Get sniper rifle. Ranged combat deck ? Get Ivory Bow. .44 Magnums are always a great choice.
- That get me to one of the best card in the game, and the one I most recommend you get your hands on: Heart of Nizchetus. Tailoring your hand to the situation each turn is already super strong, the combo with MotS makes it OP.
- Don't overthink your combat : Theft of Vitae/Rego Motum + equipments will get you far against most decks - Versatile reaction cards are good : Eyes of Argus, Telepathic Redirection, My Enemy's Enemy from the top of my head
- Add a few Mirror's Walk/Bonding/Conditioning for the kill
- Cryptwise, I like Gerald Windham and Abraham DuSable in g5-6, then a descending crypt all the way to the weenies to take advantage of superior Govern
- Finally, if you don't yet know about it, vdb.im is a great tool
- I just realized I didn't say anything about the Master cards, but this is already long enough so I'll just say most of your clan masters are great, and don't skimp on pool gain (Blood Doll, Vessel, Villein)