Hii, I am just preparing whatever is mentioned in the IRCC checklist. and if I do not have the proof, I am writing letter of explanation along with some other related documents. The list looks pretty simple, but it takes lot of time to prepare it
Apart from the application forms, we need
PCC
we should not do upfront medical for sponsorship
marriage certificate
applicant's educational documents, employment docs, passport and other govt proofs if its required for your country
Sponsor's PR card, employment proofs, bank stmt, T4, passport, etc
And collect as much as solid documents to prove your relationship such as photos(if your marriage is not one year older or you dont have kids, you need to collect strong evidence to prove your relationship) , social media post, journey tickets, email receipts for hotel check in or for order delivery(gifts ordered for spouse), bank statement which shows transaction between husband n wife, if you have joint bank account or insurance policy, property or utility bill doc etc..
I might have missed something, pls go through the checklist.