Welcome!
After just playing through a few arena combats, you might find it fun to play through the several encounters in the
Postcard Contest.
The Infinite Arena is also worth playing with, too.
These alone should keep you busy for a while.
But don't forget the drop tables inside the Legacy Edition and
Decks of Destiny boxes. You can use those to randomly generate labyrinths with nasties to slay.
The
Labyrinth Cards add another tool to generate and record labyrinths.
As great as TFT is solo, though, it really gets better when playing with others, especially when wizards are involved, since the guesswork it brings to the table creates tension you just can't get when playing alone.