Good concept but there are several issue that will need to be tackled:
1) The game quickly become repetitive and dragging because most tic tac toe game will end up in draw, and drawing does not help to progress the game in any meaningful way. I suggest to implement something that make draw more meaningful (both player take 1 damage, tile type that activate if draw, etc)
2) The double placement tile is absolutely too strong due to the small size of the board.
3) Lack of player agency between each battle because there are no upgrade choices (decided by RNG).
4) Probably an oversight but HP reward does not heal you up, and I have yet to discover any way to recover HP, making that reward completely useless.
Overall the game have potential but balancing and more content update will be needed to give it more replayability.