What kind of party system is normally associated with first-past-the-post voting?

Answer is two-party system.

Explanation:

The first-past-the-post voting is a type of voting system where an individual is considered as the winner of an election or is elected simply because he has the highest number of votes.

Other examples of voting system are run-off and preferential voting.

Subsequently, a two-party system is a type of party system electorates voted massively for only two major parties during a general election, and these two major parties capture almost all the seats of the legislature. The party with the highest number of seats in the legislature is considered as the majority, while the other party is the minority.