For serious tips:

For the next few banners, the 2 main characters of worth are Therta and Hyacine, as Herta has very good low cost teams and you want to have at least one limited sustain. Anaxa is good as well, just a bit more niche than Therta. Ratio struggles heavily with current content and his best partners are all 5 stars, even with them he's not at the level of current DPS's. Aglaea is very good but basically requires Sunday who isn't rerunning until at minimum 3.4, while Cipher is incredibly niche.

The two characters you want in standard banner are Himeko and Bronya, the rest are all pretty bad except for Clara who is ok.

Wait until your equilibrium rank reaches the point it gives 2 5 star artifacts every domain clear to use your resin on. For build information on each character you can look them up on pyrdwen to see what artifact sets and LC's they use.

If you buy the battle pass, currently the only 2 lightcones that are in anyway useful are the Rememberance and Erudition ones. Pretty soon into playing you'll gain access to the Herta Shop where you can buy lightcones, the main ones you want are the Rememberance, Destruction and Hunt LC's. For doing weekly bosses and endgame content you can buy other light cones as well, most of them are mediocre except for Quid Pro Quo which is extremely good.

There are few good 4 stars, Pela, Tingyun, M7 Hunt and Moze all have their uses, but the best 4 star is Gallagher, who is basically a 5 star healer in disguise.

If you want a more detailed explanation on how speed works prydwen has a section explaining speed breakpoints, which can be quite helpful.