Why have parties anyway? What do they do? (Focus on the 3 sections in the intro; the rest you can explore on your own)
Open Primary Elections Political Party Innovation Primer 4 (reading)
List PR and advantages and disadvantages of the system.
Open, Closed and Free lists in Proportional Representation systems
Candidate Vetting Mechanisms in Latin America (focus on executive summary and then browse table 1)
These case studies cover how people vote for parties, how party leaders are picked, and information about party's ideologies and party systems in different countries.
Open list in Brazil (written)
Moving from a single party system to multiparty (with no changes in the system) in South Africa
Voting 101: What is Australia’s preferential voting system and how does it work?
Voting in Proportional Representation Systems with ranked voting by party list or individual
Party leadership changes and challenges: a quick guide (written)
The Role of Political Parties on Women’s Participation and Representation (this can also be used to promote ethnic, religious, or linguistic representation.
Want to compare election-related statistics and data covering more than 200 countries and 11 different topics quickly? Of course, there's a dataset for that.