Welp..........
Is there like any guide to like know which units have advantages against which units, how much certain upgrades are more worth it than the others or stuff?
Main goal is to understand the economy. Your core research should always be raid size and all your best units(even girls) should actually be in raid.
Never speed up researches early on - starting research is way better investment. There are finite amount of them and most of them are massive upgrades so doing as many at same time as possible is important.
Aside of that spam 6 goblins in rooms left/right from Reina BUT leave Reina solo in her room. This strategy allows her to solo tolerable amount of pressure while the 3 goblins to the left/right take most of their lane pressure away from her while being buffed.
What you need to understand is that Reina buff makes goblins essentially on par with most other creatures until midgame. That makes their spam in rooms left/right of her incredibly powerful due to how easy it is to get seedbeds.
Usually at least one side partially survives.
All red resources should be invested into developing Reina > other Girls > Monsters in raids and only once you reach the point where you are done with those should you start to reach the point where you actually NEED the upgraded units defending you.
Other research priorties after raid are:
Training Reina/Girls(this is a one and done super early game) > Spammable skills(those are literal difference between wipe and win without even full goblin loss, bosses without those are often nigh impossible, boss fighting 1 buffed full HP goblin can often take ~30-50% HP damage from your skill spam alone) > New units - more power in raid is good and those are usually cheap researches so don't neglect those even though I give them not so high priority > Traps(do NOT use them, at worst only use one near entrance, anything else is not worth for a long time, but each trap is a potential resource gain which you can eventually sell to gain back the cash you spent and everything beyond that is profit)
As for caps:
1 money cap is enough for a long while, seedbed caps should always be maxed since you easily gain full cap from 0 in 1 raid, red cap wants level 2 ASAP or you will not be able to upgrade most stuff without waste.
The game is all about snowball effect - you either keep growing and surpassing enemy through sheer economy OR you get infinitely punished with barely any progress.
The strategy above allows you to reach ~half research tree(entirety of what is available to you) completed by end of chapter 2 after which it becomes much easier since you can dedicate more resources to defenses rather than having to keep rushing the research tree.
Once your economy is this solid - the rest of the game is a cakewalk on normal difficulty.
The ogres as mentioned above are very overpowered with stats way above the tier when they unlock, hence once you start deploying them - you essentially start having entire rooms worth of Reina stats and it only gets easier from there.
The top 2 units after that are only slightly stronger than ogres stat wise... and in terms of bulk the ogre even surpasses them due to the damage reduce passives.