Yeah it does seem like it'd be hard to escalate levels while still having more than one card in play, which is what would be needed for combos and just fun interactions in general. Exponential power is a good idea. Mechanics that let you play certain cards, like ygo (I don't play it so I don't really know tbh) ie. "(Backup): if this dies, you may play up to two level 1 cards." would help. Also 0-level cards can also serve as single use action cards (like instants or spells or something) so those can also be used to bring out more cards from your hand, ie. "(Cast): when this enters play, you may discard this card along with another from your hand and play a level 2 card."
hm yeah I might mess around and make some basic utility cards!
I saw on twitter someone was making cards that mess with the Materials mechanic (where you can play a card facedown and turn it into a blank, can't have actions, level 1 sacrifice token) and I think that's a good direction! I know I built this game with more Yu-Gi-Oh in mind than, say, MTG lol
That sounds like it'd work well. Other cards could use that mechanic to convert in-play cards to materials or vice versa.
This game gives me Dvorak and 1000 Blank White Cards vibes because of how community driven the card making is, which is a great thing. If anyone needs inspiration, there are Dvorak decks online which are a treasure trove of neat mechanics and ideas (try http://www.dvorakgame.co.uk/index.php/Infinite_Dvorak_deck).