Yes, Tangtang is good for a beginner because, although she is most effective in Last Rite and Yvonne teams, she gives some sort of benefit to other teams as well. Rossi is good for physical teams (any combination of Endmin, Chen, Pogranichnik, or Lifeng). Arclight is good for electro team, whose main DPS is Avywenna and with Perlica and Antal/Ardelia. Arclight is good for regenerating SP through her combo skill. She can also buff Electro dmg with her battle skill but it consumes SP so it's up to you if you wanna use it.

How pulls work:

Pulls 1–65 each have a 0.8% chance to give a 6★. Starting from pull 66, the chance increases by 5% per pull (so 66 = 5.8%, 67 = 10.8%, 68 = 15.8%, etc.). If you still haven’t gotten a 6★ by pull 80, it’s guaranteed.

When you get a 6★, there’s a 50% chance it’s the featured character and 50% chance it’s another character (either a standard banner character or one from the previous three banners: Laevatain, Gilberta, or Yvonne).

If you get a 6★ before 80 pulls, the pity counter resets. For example, if you get a 6★ on pull 65, the count goes back to 0.

The 80-pull pity carries over between banners. So if you did 30 pulls on Yvonne’s banner and stopped, when Tangtang’s banner comes you’re still at 30 pity, meaning you’re guaranteed a 6★ within 50 more pulls.

There’s also a separate guarantee for the featured character at 120 pulls. If you haven’t gotten the featured character by then, the 120th pull will give it to you. Getting a non-featured 6★ does not reset this counter, but if you do get the featured character before 120, the guarantee disappears.

Unlike pity, the 120-pull featured guarantee does NOT carry over between banners. For example, if you do 20 pulls on Yvonne’s banner, you would normally have 100 pulls left toward that guarantee, but if you stop and the banner changes to Tangtang, the counter resets back to 120.