Upvote:4
From your question and other information you’ve provided in comments, if you reapply you can probably fix the deficiencies around your relationship to your cousin and your educational ties by providing better evidence to address the points raised in the refusal letter.
What you can’t do quickly is overcome the discrepancy between your statements in the application that you have no income or savings, but spend £180pm. This information is contradictory, and UKVI don’t understand how the two ‘facts’ can both be true. You’ve said in your comments that this money comes from your father in cash as and when you need it. So the answer to ‘what to do’ (although it clearly won’t be what you want to hear), is improve the evidence relating to the other refusal reasons and start getting your cash allowance paid from your father’s into your bank account. Wait until you have at least 6 months’ statements demonstrating this before you apply again.
Do not be tempted to reapply immediately with a different monthly spend figure - that’s a recipe for disaster. UKVI will refer back to your first application and ask themselves whether you are massaging the figures to increase your chance of success.
IMHO, given that the refusal reason relating to the £180 was factually correct there is very little, if not no, point in lodging a complaint in an attempt to get this decision overturned.