As you play through the game you will get fans. More tracks unlock as you acquire more fans. You need to play each track available in each event at least one time offline. Here is a list of all the available tracks broken down by event:
Pro / Battle Race
Lighthouse Loop
Great Dragon Road
Rocky Road Speedway
Aviator Ranch
Boathouse Bay
Forbidden Fortress
Cannon Crossover
Stunt
Crimson Gorge 1
Paradise Pipes 1
Crimson Gorge 2
Paradise Pipes 2
Crimson Gorge 3
Paradise Pipes 3
Dash
Badlands Freeway 1
Coastal Highway 1
Badlands Freeway 2
Coastal Highway 2
Badlands Freeway 3
Coastal Highway 3
Badlands Freeway 4
Coastal Highway 4
Smash
Cloudtop Temple 1
Desert Drainage 1
Cloudtop Temple 2
Desert Drainage 2
Cloudtop Temple 3
Desert Drainage 3
Trick
Sunset Harbor
Perilous Peaks