Interesting way to play.
Once the creatures of Player 2 are in, can they still be killed, pushed, teleported, etc.? Does player 2 need to keep them in?
If yes, then I guess player 1 is mainly going to throw Attack spells and traps.
Also, what do you mean by "no rounds". Both players can play whenever they want? This might create a lot of confusion.
When is a wave over? When the 30 mana of player 2 are spent?