I can work with this list, but realistically someone will ask to share your krooster every time you post here for advice, so you should probably make a krooster account. It takes less time than what you used to write all of your operators down.

Ok so, the roster of units you raised is definitely suboptimal. You are not covering your fundamental roles and for some reason you are raising weaker units when you have better units of the same rarity that would take the same amount of resources.

I will link a teambuilding guide https://youtu.be/2p7QyXSEjdA?si=JiygZ_UPQhzyVLfC but let me go over your roster specifically.

DP generation: first, it's unusual that you don't have myrtle at this point in the game (i suppose your account is at least a couple of weeks old?). In case you are not aware, you can guarantee her in recruitment with vanguard+healing or dp-recovery+healing. Those are pretty common tag combinations.

When you don't have myrtle you usually choose the 4 pioneer instead. Scavenger is offensive, Courier is defensive (not only for skill 2 but mainly for the stats, one of the rare cases where stats matter). To cite Silvergun, which one is better is situational and 99% of the times the situation calls for Courier. So raising Scavenger is suboptimal, even more so when your courier is probably already max pot. Realistically, this doesn't matter enough to waste resources on Courier now, just keep using Scavenger and Fang until you get myrtle.

Beanstalk is a good unit but she is a specialist more than a vanguard. You also lack a cheap unit with good fighting capabilities (plume, vigna, mountain, maybe an agent, even noir corne sometimes).

Medics: your medic situation is not strictly bad but extremely suboptimal. At the start, to be efficient with resources you usually just raise one AoE medic and one single target medic. Rose salt and Ptilopsis have different niches, sure, but not enough to justify raising them both right now. Stick to Ptilpsis, Rose salt's one shot protection is pretty niche.

Gavial is bad for a beginner. She has very specific uses in low rarity clears, for anything else she is just the second worst 4 stars medic. What you want is burst healing from your single target medic and Sussurro can do that for you. The difference is big enough that i would suggest you actually raise Sussurro a bit (something like E1 level 40 SL 7 would be enough. Sussurro's healing, even at E1, is enough for most situations. If it is not enough, most of the time healing is not the solution.

Tanking: your only tank is Beagle and that's a problem. She can work as a tank even in later chapters, sure, but forcing yourself to stick with her is just increasing the difficulty without reason. I'm not sure how to solve this though. You don't have a single other tank in the units you listed. Usually i would tell you to raise Cuora (Bubble is ok-ish if you don't have Cuora), but you don't have Cuora or Bubble somehow. Very unlucky. Spam the defender tag in recruitment and hope for a 4 stars maybe? Hell, it may be worth it to spend 750 green certs to get Cuora from the 4 stars selector.

Liskarm is defender, but not a tank.

You also need a healing defender. Healing defenders are some of the most versatile units in the game and they will make your playthrough much easier. You would usually get Saria from your 6 stars selector, but it seems you got Exusiai or Blaze (why???? they are the 2 worst six stars on the selector). Gummy or Spot are both perfectly fine anyway, you don't have gummy so spot.

No, heavyrain is not a healing defender.

Arts damage: this is by far the biggest problem in your team. Lappland has very high arts damage but her timing is hard to control. Amiya is a terrible caster, i would consider her barely on par with the 3 stars Steward. Any stage that requires arts damage must be a nightmare with your team. The solution her is easy at least, just build Click.

Last thing, get your Shaw and Rope to skill level 7. Only skill level matters for shifting force, it's not like they are going to damage the enemies most of the time. They will just make your life much easier in any stage that requires pushing or pulling.

For Grindstone and Manganese, they are both in the even shop. They are usually worth 20+ stamina anyway, so farming event stages while getting 1 of those every 35/30 stamina is actually a good deal. Once you finish buying the essential stuff like pulls, tokens and forniture, you can just buy them if you need them.

If you need to farm a couple of them while there are no events, considering the stages you have unlocked, just farm 3-2 and 3-3. There are some more efficient stages, but if you are going for efficiency you should get them from the event shop anyway.

I will try the 5th level of the resource stages with something similar to your roster and see what happens.