For undergraduate courses: five credits (excluding languages like Hausa, Igbo, Yoruba) but including English and Mathematics will qualify you for a foundation which means you can study over a period of four years. A few colleges have what you call Year1 degrees which are essentially teaching both the foundation and yr1 of a University within a year. These are suitable for more mature students and those with stronger grades. Some are happy to go ahead from age 17 as long as grades are very-very good. For three year degrees, you will need in addition to WAEC/NECO good grades at Advanced levels in three subjects or OND with very strong passes or first year of a Nigerian University. You can also use a degree foundation certificate but DFP are on a case-by-case basis. Some HNDs are qualified for entry into Yr2 or Yr3 depending on level of passes. For Postgraduate courses, you will need a very good second class lower. Many courses require upper class while some prestigious Universities will require no less than upper second class. However, those with 3rd class or HND can go for a Top-Up degree course.