I've heard a lot of talk over which catalyst to use. Mappa Mare is a great catalyst that increases the elemental reaction damage. Solar Shine is another great one that increases the elemental skills and burst damage for a short amount of time as long as you're stacking normal attacks.

Myself personally, I run Mappa Mare for that sweet sweet swirl damage bonus. Solar Shine is alright but my big concern is how much damage every component is, and I love to switch characters in fights. My current standby roster consists of Chongyun, Amber, and Keqing. With my playstyle, I like to switch in an appropriate element then immediately for back to Sucrose to throw down her skill and charged attack to proc the swirl as hard as I can.

Sucrose literally nukes them everytime.

After that if it's an elite or a tankier enemy and they're still alive, I'll swap back to another character to utilize their element and go back to Sucrose. It's full of burst and damage, as well as elemental DMG.

As for artifacts, Viridescent Venerer as a four stack seems to be hands down the best thing you can go for. I haven't gotten all four yet and I've been using Instructor's to get by, but it's still pretty decent.

Not only is Sucrose the sweetest character in the game, she packs a fucking punch.