It should be clear at a glance to the consular officer what written documents you are presenting and what they signify. Lengthy written explanations cannot be quickly read or evaluated.
Applicants from countries like Nigeria with economic challenges or from countries where many students have remained in Canada as immigrants will have more difficulty getting visas. Statistically, applicants from those countries are more likely to be intending immigrants. They are also more likely to be refused based on the lack of adequate funds available for their study in Canada. To overcome this challenge, it is important to present financial statements that show you can afford to pay for your one-year tuition and you have enough left for accommodation, transportation, feeding and miscellaneous expenses.
Your primary purpose of coming to Canada should be to study, not for the chance to work before or after graduation. While many students are permitted to work for 20hrs per week, such employment is incidental to their main purpose of completing their Canadian education. You must be able to clearly articulate your plan to return home at the end of your program. If your spouse and children are also applying for accompanying visa, be aware that you have to prove to the consular officer that you have enough financial resources to pay for your children’s education in Canada and not rely on employment in Canada to support their education. You also need to address what your spouse intends to do with his or her time while in Canada. Working and attending school part-time are permitted activities.
If your spouse and children are remaining behind in Nigeria, be prepared to address how they will support themselves in your absence. This can be an especially tricky area if you are the primary source of income for your family. If the consular officer has the impression that your family members will need you to remit money from Canada in order to support themselves, your student visa application will almost certainly be denied. If your family does decide to join you at a later time, it is helpful to have them apply at the same post where you applied for your visa.