I only knew my wife for 8 months, when we married on my second trip to ever see her. I was only divorced for 3 months from my previous marriage when we married. My application was successful in only 6 months start to finish, no interview even when IRCC estimate said 24 months at the time. This is what I provided as proof of our relationship.
1. 20 pictures in a single PDF with a description for each.
2. 1/2-page letter from myself and 1/2-page from my wife with a brief description of our relationship.
3. Phone and text logs.
4. 2 letters from my family and 2 letters from wife's family in support of our relationship. Very short letters. Just a few sentences each.
5. Trip receipts, Wedding receipts etc…
6. Proof of support.
And just the other basic requirements they ask for.
We also provided a letter of explanation for two questions. My wife had no idea of her parent's birth or death dates, The other was to explain why I was divorced and remarried in a 3-month period.
Provide strong evidence, stick to relevant facts. Do not write a boring novel. More than two pages is a boring novel.