The #1 thing is for you to decide what damage type you’re using. Your gear says cold, and TSS is a fantastic cold skill. But the skill you’ve most heavily invested in is PB, which does vitality and bleed (with a bit of cold and chaos from Nether Edge). And your devotions include Assassin’s Mark, which is a key devotion for physical or pierce builds, which is not what you’re doing (though you do have a pierce component on your off-hand for some reason). Pick one damage type (maybe two when you’re more experienced and know what you’re doing), build around that. Skills, gear, devotions, everything.
As usual for new players, you’re a bit under-invested in your mastery bars, but not too badly so actually. Your resistances are also a bit low, though how much so depends on whether you’re in Elite or if you’re still in the late stages of Normal/Veteran. Components can help you out a fair bit, regardless. They’re plentiful, so use them on every piece of gear. Your relic is notably bad - check the faction vendors for blueprints, once you meet Hyram in Malmouth (if you have AoM) he’ll have more, and you can do the Origin of the Slith quest from Kasparov if you haven’t already for another random relic blueprint.
Attributes - when in doubt, put everything in physique.
Looking at the build compendiums, I see there is a spellbreaker using both PB and TSS here, so maybe that could be useful to you as an end point to work toward. However PB won’t do cold damage until and unless you find and equip that specific level 94 off-hand (and if you only have the base game, it’s not available at all). The usual practice would be to level using some completely different setup, then respec at 94; I find that absurd and don’t play builds like that, but do what you like.
A more common approach to cold spellbreakers is to focus on TSS, and use Ring of Steel with the Ring of Frost transmuter alongside Night’s Chill, Pneumatic Burst, and Shadow Strike on the Nightblade side. Very fun, and you might get blue level 58 drops (the Eastern set) that support it nicely for a while. If you do that, you’d want to pull the points from Phantasmal Blades and put them into your arcanist bar, TSS, Frozen Core, Star Pact, and Maiven’s. (You’re gonna need a lot of skill points, obviously…). Warning, although it’s a lot of fun, this tends to be a bit on the squishy side and isn’t necessarily ideal for a first character.
RR is the key thing to aim for, so if you respec to cold, you’ll want Elemental Storm, Rumor, and Viper. Blizzard and Whirlpool are nice damage procs.
If you’d rather keep transmuted PB, you’d want to set up around vitality damage. I’ve never done a PB build myself, but I’m sure you can find ideas in the compendiums. And vitality builds are fairly common so that can help you with devotion setups (Will of Rattosh would be a top priority, assuming you have AoM). Vitality spellbreaker has no mastery RR support, and the arcanist mastery won’t be doing much for you at all. I see it’s not even in the Missing Builds Workshop, so I would not recommend this approach. Maybe do something with pierce damage using the untransmuted PB?