This was a straight forward map to win with 3 Stars on first attempt. I had taken the extra card slot and one gem was required to revive my Avatar.
The cards I had used were;
Towers - Mana (7), Tesla (6), Javelin (8), Anti-Air (7) and Poison (9)
Spells - Thunder Moose (6), Clarion Call (8), Artillery (6), Healing Spring (9) and Frost Storm (4)
With this map, it is about starting with the minimum number of damage towers plus the three Mana towers. Then gradually upgrading the Card Sharp ability of the Mana towers and planting further towers leading away from the engage point where all tracks intersect as the battle unfolds.
Do not lose focus from using your limited use spells, namely Artillery and Frost Storm, throughout the battle. You will see that by the end of battle, I had used up both of these two spells.
The screenshots below will help with the approach.