Higher education serves as an important vehicle for social mobility, particularly for students from disadvantaged socioeconomic backgrounds. However, achieving equitable outcomes in college access and success remains challenging, influenced by various layers of contexts, including personal, institutional, and policy dimensions. Despite increased attention and support for first-generation college students, significant disparities persist in retention and completion rates compared to their continuing-generation peers. Understanding these disparities and the complexities facing first-generation college students requires a close examination of the variation within the population. This dissertation aims to understand the complexities of the college experiences of first-generation students through three interconnected studies. This dissertation not only investigates heterogeneity within the first-generation college student population but also specifically seeks to explore how institutional-level factors affect first-generation students and how the interaction between institutional-level and personal factors shapes college experiences and outcomes. The first study investigates how high school contexts impact college choice for first-generation students, particularly leading to college undermatching. Additionally, this study contributes methodologically significance by demonstrating the inclusion and control of college selectivity when studying college undermatching as an outcome. The second study explores the differential effects of college undermatching on postsecondary outcomes for first-generation and non-first-generation students, including GPA and retention rates. The third study examines how postsecondary outcomes vary between students with and without cognitive disabilities, stratified by first-generation college student status. The findings of this dissertation study challenge the common notion of the first-generation college student population as a homegroups group. Results emphasize the importance of tailored support mechanisms at the institutional level, including secondary and postsecondary settings. By recognizing the diversity within this population, institutions can better address the unique needs of first-generation students and promote equitable outcomes.