((So since this game has so many people, I will give until the end of the day before moving on to the next class. I'd suggest you prepare some 0-star Card ideas in advance so that you'll have something ready to go when the turn drops!
In the mean-time, I have my own advice and reasonings on the Core Cards:
Sallow Grimpling: While it does lose to the Iguana, or even the Infantryman, can be useful in the fact that, well, it can buy time. The advantage of being able to put two weak cards on the field instead of one slightly stronger card cannot be overstated.
Learned Sage: Not much to note here. A card draw with enough body to tank the ranged shot from an infantryman. That does however provide it an opening to be buffed by the Engineer and then healed via Drenc.
Drenc: A versatile spell. Having direct removal, even if it is an exceptionally weak form, is always useful, and its ability to keep your tanks alive cannot be underestimated either.
Elven Engineer: While the primary uses of this card have of course been sussed out, one thing that is to be noted, is that the effect does not say "another card", merely "a card".
Infantryman: This one has already been figured out. Very straightforward card.
Red Shirted Space Cadets: The cadets may not seem like that strong a card. Heck, even the French Soldier would at least accumulate buffs over time. The difference to make note of though, is that playing the second copy doesn't count towards your cards-per-turn limit. After all, if it did then it... literally wouldn't have an effect at all, and that would be horrendous card design if I made a card weaker in order to accommodate an effect that literally had no functional purpose.
Spirochete: Only real thing to note is that the effect applies regardless of if it's attacking or defending.
Star Pistol Waifu: So, the reason why this one is 1/2, despite not even guaranteeing you a star while Honoka (who had the same stats) did, is that you can't buff passive star-gen, but you can increase a cards number of attacks, meaning that Star Pistol Waifu could be given any number of attacks, and thus generate that many Stars every turn.
White Noise: It was honestly more powerful that reasonable in its previous form. This new form certainly has much less of a direct use, but this card can effectively be used as a way to attempt to keep your current advantage, rather than risk your opponent drawing a card that breaks it.))