Thanks for the tips.
I am currently using Lisa as the DPS as she auto-targets and I don't have to worry about chasing every single enemy down. I use Amber's Fire doll and then use Lisa to cause elemental reaction. Now that I have Barbara, I use her to wet the enemy, then Lisa to Superconduct. Barbara also has that book weapon which gives 24% ATK to switched character. Not sure if ATK even affects reactions, but I'm still working through it all.
I'm reading that Vaporize and Melt seem to be the best elemental effects in terms of damage, so guess I'll work into that going forward.
I don't want to inundate you with a ton of info all at once, but the biggest component to most elemental reactions are a combination of character level in relation to enemy level and elemental mastery (a stat). Vaporize and Melt are considered the best because not only do they use those two factors to scale damage, but they also factor character Attack stat into the equation AND can crit (this is the big difference). When I was just starting out, I found that constantly swapping back and forth between Barbara and Lisa and just mashing their attack button was a very viable method of taking out small groups and flying enemies due to the electro-charged reaction not having any internal cooldown.
It's worth noting that you're going to get a few free characters as you progress. Unfortunately you've already missed quite a few free characters given out via events, but I'm sure there will be more as time passes. At any rate, I think you're up to get 2 more Barbaras and a Xiangling (pyro polearm user). Eventually the main character will learn how to swap elements between Anemo (air) and Geo (earth). When you get duplicates of characters, you also obtain an item that lets you increase their "constellations" which will make them stronger in various ways. Usually the good ones are at 2/4/6 constellations. 6 is the max you can improve a character as of now.
Your biggest weakness at the beginning of the game is that you don't have a particularly strong DPS carry character (one that stays on the field most of the time and does big damage). Luckily (or not), these are usually the roles of the featured limited 5* units on rotating banners. If you save up, you can pretty much guarantee getting one of them. There is a pity mechanic for the wishes in this game. By 73 pulls you hit "soft pity", meaning that your chance of pulling a 5* goes up to like 40% or so. If you have absolutely horrible luck, the max hard pity is 90 pulls to guarantee you a 5*. On the rotating character banners, this 5* can only be a character, and has a 50/50 shot of being the focus character. If you get unlucky on the 50/50, the next 5* you pull on that banner will guarantee the banner character. This also saves pity progress across banners of the same type, so if you roll on the Eula banner (the current one) and get to 70 rolls, then the next banner comes around (Klee), you only need to roll a max of 20 to hit the pity. A lot of us will roll for this on purpose to "build" pity to guarantee we get a particular character we want on a future banner. You can alternatively just save 180 rolls worth of currency to guarantee yourself even in the worst of luck. I don't think anybody in this thread has ever had to do 180 rolls for a character though.
Eula, the current limited 5* is very strong, but is a physical damage type, which is a heavily resisted damage type to anything that isn't a human enemy. She also has no support capabilities, so once she leaves the field she's not contributing anything to to the team.
Klee is the next banner, who is still one of the top DPS characters, and she's Pyro which is the best element in the game for all sorts of reasons. Either of them would be a big improvement to your team though. Past that, we know there will be a 5* Anemo (air) sword user that looks to be mostly support, then likely some new characters that are still relatively unknown.
Well, so much for not hitting you with too much info. Ask away if you have questions, or just ignore it entirely and play however you want.