Complete more requisites to unlock new contract types
Complete several requisites of the same team to unlock new contract types with the team. In total, there are four contract types: Rookie, Challenger, Expert and Master.
If you complete one requisite, you will unlock a Rookie contract. However, if you complete two requisites for the same team, you will then gain access to a Challenger contract with this team. If you complete three requisites of a team, you will be able to sign an Expert contract and if you complete all of the team's requisites, you can sign a Master contract.
Number of GPs in a Season, objective, rewards and team missions
The different contract types feature a different number of GPs to be played during a Career mode Season. When signing a Rookie contract, you only have to complete 4 GPs to complete a Season. Whereas in Master, there are 20 GPs in a Career mode Season.
The higher is the contract type you have signed, the more difficult the season objective given by your team will be. Also, the rewards earned by completing the season objective change according to your contract type.
Finally, as you sign a new contract type, you will unlock new team missions to complete along the other team missions you haven't completed yet.
Differences between the Teams
The Team requisites of the F1 teams are all unique and different. Also, some teams don't offer Rookie, Challenger or Expert contracts. For instance, you have to complete all of Mercedes' requisites to sign your first contract with them as they only accept drivers with Master experience. Same goes for Red Bull, they only offer contracts to drivers with Master experience.