Well, I contemplated about a EBTCG, and working developing a new ruleset for CLTCG (now non-existent) I learned a bit.
1. Attacking cards
Card Types: Heroes (helpful characters in Mother), Villains (anyone “evil”). Covers pretty much everything.
Sub-types: Human, Insect, Alien, Plant, etc. Allows for more strategy
Icons: Can represent if PSI is used, and equipment types (guns, yo-yos, bats, etc.)
Stats: ATK, DEF, HP, SP. Why am I not using PP? I’ll elaborate later. Used SP and HP could be denoted with counters.
Skills/effects: Some cards always have skills. Like Boney’s “Sniff” could let you see an opponent’s hand, or say Starman has a PSI skill. Some cards could also utilize this for bonuses. Using a skill takes away skill points.
2. Equippable Cards
Weapons: Add ATK bonuses. Could be stacked.
Accessories: Add DEF bonuses.
Skills: Anything non-PSI. Can be almost anything. Can be used on PSI-users and non-PSI users alike.
PSI: Any existing PSI skill. Can be equipped to PSI users only.
3. Places
Places could add bonuses to primary types and and sub-types. The could also have certain effects, like discarding cards, etc.
4. Event Cards
Provide many effects.
Just some ideas.