Focus on Valley and Lagoon first. These tracks are shorter (usually 30-45 second laps). Shorter tracks mean faster medal acquisition.
If you type that phrase into Google, you are likely looking for a cheat code, a save file, or a secret button combination. Here is the hard truth: Trackmania Turbo has to unlock tracks. Ubisoft designed a linear progression system that forces you to earn medals.
"There is a Konami Code for Turbo." Reality: False. Entering ↑ ↑ ↓ ↓ ← → ← → B A on the title screen plays a sound effect, but it does not unlock tracks. It is just an easter egg.
In the Blue and Red series, look for tracks labeled "Multi-lap" (usually 3 laps). These are terrifying for beginners, but here is the secret: Because you have to do 3 laps, the Bronze time is extremely forgiving. You can crash twice per lap and still win. Knock out multi-lap tracks immediately for easy unlocks.